Module 1 – Background
INTRODUCTION TO EPIDEMIOLOGY: THE EPIDEMIOLOGIC APPROACH
Required Readings
Coggon, D., Rose, G., & Barker, D.J.P. (2007) Epidemiology for the Uninitiated (4th edition). British Medical Journal. Retrieved May 22, 2012 from http://www.bmj.com/about-bmj/resources-readers/publications/epidemiology-uninitiated
Centers for Disease Control and Prevention. PulseNet. Retrieved Retrieved May 22, 2012 from http://www.cdc.gov/pulsenet/
Centers for Disease Control and Prevention Timeline for Reporting of E. coli Cases. Retrieved February 26, 2011. http://www.cdc.gov/ecoli/reportingtimeline.htm
OMRAN, A. (2005). The Epidemiologic Transition: A Theory of the Epidemiology of Population Change. Milbank Quarterly, 83(4), 731-757. doi:10.1111/j.1468-0009.2005.00398.x. Retrieved Retrieved May 22, 2012 from: http://onlinelibrary.wiley.com/doi/10.1111/j.1468-0009.2005.00398.x/pdf
Principles of Epidemiology. Retrieved Retrieved May 22, 2012 from University of Illinois at Chicago Web site: http://www.uic.edu/sph/prepare/courses/ph490/resources/epilesson01.pdf
DNA Fingerprinting. Retrieved May 22, 2012 from cphp.sph.unc.edu/focus/vol4/issue4/4-4LabTechniques_slides.ppt
Module 1 – Multiple causation
INTRODUCTION TO EPIDEMIOLOGY: THE EPIDEMIOLOGIC APPROACH
Multiple causation refers to the prerequisite that more than one factor must be present for disease to develop in a host. When a factor must be present for a disease to occur, it is called the agent of that disease. For example, HIV virus is the agent of AIDS. Although an agent is necessary, it is not sufficient to cause disease. Factors that may affect the development of disease can be classified into two groups:1) host factors and 2) environmental factors.
Host Factors
The state of the host is affected by genetic factors and past environmental exposures. These factors can affect the susceptibility of a host. For example, sickle celltrait (a genetic factor) is associated with a decreased risk of malaria. Past environmental exposures that affect susceptibility include specificimmunity, which is a state of altered responsiveness to a specific substance acquired through immunization or natural infection. Other environmental exposures be chemical in nature (e.g. cigarette smoking, asbestos).
Environmental Factors
Environmental factors can be categorized as biological, social, or physical. Biological factors include the agent of the disease, the place where the agent lives and multiplies (e.g.human beings, animals, soil), vectors that transmit disease (e.g. flies andmosquitoes), and antibiotics. Social factors include the technical level of medical care, health codes controlling environmental hazards, and social customs. For example, the custom of serving chicken tataki (undercooked chicken) may expose an individual to infectious agents, such as Salmonellaor Campylobacter. Physical factorsinclude heat, light, air, water, radiation, gravity, atmospheric pressure, andchemical agents. When weather conditions cause masses of air pollution to be trapped for several days, inhabitants can be exposed to noxious substancesthat can lead to chronic diseases.
Ecologic Models
Ecological models have been developed to illustrate the ways in which these interactions influence the occurrence of disease. Two commonly used models include the epidemiologic triangle and the web of causation.
The epidemiologic triangle consists of three components: host, environment, and agent. A change in any of the components will affect the equilibrium by increasing or decreasing the frequency of disease. For example, individuals exposed to the “common cold” virus may not all become ill because of differences in nutrition or stress (host factors).
The web of causation is often used to explain conditions that have not been linked to specific agents. In this model, more emphasis is placed on the multiplicity of interactions between the host and environment, rather than the agent. According to this model, conditions develop as a result of chains of causation in which each link represent a complex web of antecedents.
Module 1 – Outbreak Detection
INTRODUCTION TO EPIDEMIOLOGY: THE EPIDEMIOLOGIC APPROACH
Escherichia coli O157:H7 was first identified as a human pathogen in 1982 in the United States of America, following an outbreak of bloody diarrhea associated with contaminated hamburger meat. Sporadic infections and outbreaks have since been reported from many parts of the world,including North America, Western Europe, Australia, Asia, and Africa. Although other animals are capable of carrying and transmitting theinfection, cattle are the primary reservoir for E. coli O157:H7. Implicated foods are typically those derived from cattle (e.g., beef,hamburger, raw milk); however, the infection has also been transmitted through contact with infected persons, contaminated water, and other contaminated food products.
Infection with E. coli O157:H7 is diagnosed by detecting the bacterium in the stool. Most laboratories that culture stool do not routinely test for E. coli O157:H7, but require a special request from the health care provider. Only recently has E. coli O157:H7 infection become nationally notifiable in the U.S. Outside the U.S., reporting is limited to a few but increasing number of countries.
In the last week of June 1997, a certain state department of community health in the US noticed an increase in laboratory reports of E. coli O157:H7 infection. Fifty-two infections had been reported that month, compared with 18 in June of 1996. In preliminary investigations, no obvious epidemiologic linkages between the patients were found. The increase in cases continued into July.
Laboratory subtyping can help determine if an increased number of isolates of the same bacterial species results from a common source outbreak. Subtyping methods are based on selected biologic and/or geneticcharacteristics of bacteria that tend to differ between isolates of the same species. In a common source outbreak, however, isolates typically arise from the same parent organism. These isolates will be similar to each other with respect to these biologic and genetic characteristics and have similar subtyping results.
One subtyping method is DNA “fingerprinting” by Pulsed Field Gel Electrophoresis (PFGE). In DNA fingerprinting, the bacterial DNA is cut into pieces. The pieces are separated by placing them in a jelly-like substance (i.e., the gel), acting as a sieve, to which a pulsing electric fieldis applied. The electric field drives the DNA pieces across the gel over a period of hours. The smaller pieces move through the gel more quickly and the larger pieces more slowly resulting in a separation of the DNA into distinct bands. The bands are made to fluoresce and are read under ultraviolet illumination. This DNA“fingerprint” resembles a bar code. (Figure 1)

Figure 1. Typical DNA banding pattern resulting from PFGE.
Different DNA composition will result in different PFGE banding patterns. Bacteria descended from the same original parent will have virtually identical DNA and their DNA fingerprints will be in distinguishable. Identification of a cluster of isolates with the same PFGE pattern suggests that they arose from the same parent and could be from the same source.
Similar DNA fingerprints alone, however, are insufficient to establish a linkage between isolates and a common source outbreak. An epidemiologic investigation is necessary to demonstrate that there is a common source and to identify it. To be most useful, PFGE subtyping needs to be performed on a routine basis, in realtime, so that results are available (and reviewed) soon after a case is first detected.
Figure2. PFGE results on E. coli O157:H7 isolates, June-July 1997.

Typically, a PFGE “pattern” is defined as having the same banding pattern but including up to one band difference. By this definition, isolates #2, 3, 4, 6, and 7 are indistinguishable by these PFGE results. (Isolate #4 differs by one band.)
DNA finger printing, performed during the second week of July showed that 17 of the first 19 E. coli O157:H7 isolates from June-July were indistinguishable. They did not match any fingerprints from a convenience sample of isolates frompatients with E. coli O157:H7 infection before May.
Based on the PFGE findings, it was suspected the cases of E. coli O157:H7 infection resulted from a common source. On July 15, an investigation was initiated.
Module 1 – Natural History of Disease
INTRODUCTION TO EPIDEMIOLOGY: THE EPIDEMIOLOGIC APPROACH
Natural History refers to the course of disease over time, unaffected by treatment. Each disease has its own natural history, which occurs through a sequence of stages:
Stage of Susceptibility
During this stage,the disease has not developed, but the presence of risk factors favor its occurrence. For example, high serum cholesterol levels increase the probability of coronary heart disease and would therefore be considered a risk factor.
Stage of Presymptomatic Disease
Duringthis stage, the disease process has begun, but there are no detectablesymptoms. For example, atherosclerosis (hardening of the arteries) occurring before any signs of disease would be considered presymptomatic disease.
Stage of Clinical Disease
Recognizable symptoms occur during this stage of disease. This stage is often subdivided further for better case management and epidemiologic studies.
Stage of Disability
Some diseases resolve completely and do not reach this stage. However, there are a number of conditions that leave a person temporarily or permanently disabled. For example, stroke can lead to paralysis.
Levels of Prevention
Preventing the natural history of a disease from occurring is an important objective inpublic health. The levels of prevention include:
Primary Prevention
This level of prevention refers to altering susceptibility or reducing exposure tosusceptible individuals (during the stage of susceptibility). Primary prevention includes general health promotion (e.g. good nutrition, adequate rest, sex education) and specific protective measures (e.g.immunization, environmental sanitation).
Secondary Prevention
This level of prevention refers to early detection and treatment of disease (during the pre-symptomatic and clinical stage) . At this prevention level, it is sometimes possible to either cure disease or slow its progression, prevent complications, limit disability, and prevent transmission of infectious disease.
Tertiary Prevention
This level of prevention refers to the alleviation of disability resulting from disease and attempts to restore effective functioning (during the disability stage).
Module 1 – Mechanisms Of Disease Transmission
INTRODUCTION TO EPIDEMIOLOGY: THE EPIDEMIOLOGIC APPROACH
The method by which an infectious agent escapes a reservoir and enters a host is referred to as mechanism of transmission. There are two main types of transmission: direct transmission and indirect transmission. In direct transmission, an infectious agent is immediately transferred from one infected host or reservoir to another. Direct transmission includes not only direct contact, such as kissing, but also spray by droplets through sneezing and coughing onto the mucous membranes of others. Droplet spread is classified as direct transmission because it occurs over short distances–the droplets travel a few feet before falling to the ground.
There are three types of indirect transmission: vehicleborne, vectorborne, and airborne. Vehicleborne transmissionis indirect contact through inanimate objects, such as bedding, toys, surgical instruments, and contaminated food. In vectorborne transmission,the infectious agent is transmitted by an intermediary (usually an insect) to a susceptible host. In airborne transmission, two types of particles may be spread through the air–dusts and droplet nuclei. Dusts are particles of varying size that result from resuspension of particles that have settled on floors or bedding as well as particles blown by the wind.
Coccidioidomycosis is an example of a disease that is spread by airborne transmission of fungal spores. Droplet nuclei are very tiny particles that may be suspended in the air for long periods of time. They represent the dried residue of droplets from coughing, sneezing, or the aerosolization of infective materials.
Infectivity
Infectivity is defined as the ability of the agent to invade and multiply (produce infection in a host). An example of a disease with high infectivity would be measles; a disease with low infectivity would be leprosy. Techniques for evaluating infectivity include speed that an agent spreads through a population and proportion of close contacts who become infected.
Immunity
Immunogenicity is defined as the infection’s ability to produce specific immunity. Immunogenicity can be affected by host factors such as age, nutrition, dose, and virulence of infection.
Herd immunity is defined as the resistance of a group to invasion and spread of an infectious agent, based on the immunity of a high proportion of individual members of the group. Herd immunity is believed to be an important factor in the dynamics of propagated epidemics. Factors that are conducive to the development of large-scale person-to-person epidemics include the introduction of an agent to a population that has never been exposed previously and a large number of susceptible individuals with close contact(e.g. prisons, convalescent homes).
Incubation Period
The time interval between the exposure of an agent and the onset of illness is referred to as the incubation period. During epidemics of unknown pathogens, the incubation period is frequently used to rule out the likely etiologic agent.
Module 1 – Reservoirs
INTRODUCTION TO EPIDEMIOLOGY: THE EPIDEMIOLOGIC APPROACH
Reservoirs are defined as the living organisms or inanimate matter (e.g. soil) where an infectious agent lives and multiplies. The concept of the reservoir is important in infectious disease because the reservoir is the component of the cycle where an infectious agent can survive indefinitely. Humans are the main reservoir for most of the viral and bacterial respiratory diseases. Vertebrate animals are reservoirs for diseases such as brucellosis (from cows, pigs, and goats), anthrax (from sheep), leptospirosis (from rodents), and rabies (from dogs, bats, and other animals). These diseases that are acquired from animals are known as zoonoses.
Module 1 – Variations in Severity
INTRODUCTION TO EPIDEMIOLOGY: THE EPIDEMIOLOGIC APPROACH
An infectious disease may havea wide variety of clinical symptoms, ranging from no symptoms to severe clinical illness or death. Diseases such as tuberculosis have a high proportion of asymptomatic individuals (referred to a slow pathogenicity), while diseases such as measles have a high proportion of symptomatic infections and a small percent of severe or fatal illness. Diseases such as the African hemorrhagic fevers caused by Marburg and Ebolavirus are very severe and usually fatal. For diseases with low pathogenicity, only a small fraction of cases are often diagnosed and reported.
Module 1 – Case
INTRODUCTION TO EPIDEMIOLOGY: THE EPIDEMIOLOGIC APPROACH
Case Assignment
Your task for this case assignment:
Using the materials in the module homepage and in the background section, please address the following:
1. Define and describe the field of Epidemiology (1/2 page)
2. Define and explain epidemiologic transition and describe the factors involved in epidemiologic transition (1 page)
3. Say we suspect a relationship between a specific dietary factor and heart disease. Can you think of ways of epidemiologically assessing whether indeed the dietary factor is a determinant of heart disease? (1/2 page)
4. Which types of diseases do you think pose a greater risk for the population of the United States: infectious diseases or chronic diseases. Please explain (1/2-1 page)
Assignment Expectations
Length: Case assignments should be at least 3 pages (750 words) in length.
References: At least two references must be included from academic sources (e.g. peer-reviewed journal articles). Required readings are included. Quoted material should not exceed 10% of the total paper (since the focus of these assignments is critical thinking). Use your own words and build on the ideas of others. When material is copied verbatim from external sources, it MUST be enclosed in quotes. The references should be cited within the text and also listed at the end of the assignment in the References section (APA format recommended).
Organization: Subheadings should be used to organize your paper according to question
Format: APA format is recommended for this assignment. See Syllabus page for more information on APA format.
Grammar and Spelling: While no points are deducted, assignments are expected to adhere to standards guidelines of grammar, spelling, punctuation, and sentence syntax. Points may be deducted if grammar and spelling impact clarity.
The following items will be assessed in particular:
• Achievement of learning objectives for case assignment
• Relevance (e.g. all content is connected to the question)
• Precision (e.g. specific question is addressed. Statements, facts, and statistics are specific and accurate).
• Depth of discussion (e.g. present and integrate points that lead to deeper issues)
• Breadth (e.g. multiple perspectives and references, multiple issues/factors considered)
• Evidence (e.g. points are well-supported with facts, statistics and references)
• Logic (e.g. presented discussion makes sense, conclusions are logically supported by premises, statements, or factual information)
• Clarity (e.g. writing is concise, understandable, and contains sufficient detail or examples)
• Objectivity (e.g. avoid use of first person and subjective bias)

Module 1 – SLP
INTRODUCTION TO EPIDEMIOLOGY: THE EPIDEMIOLOGIC APPROACH
A Multistate Outbreak of E. coli 0157:H7
For your session-long project, you will conduct an epidemiologic investigation of an outbreak of E. coli 0157:H7. The grade for the SLP is based on the depth of your work and your ability to analyze the information, generate hypotheses about the source of the outbreak and mode of transmission. This means that the student is focusing on those factors of importance to disease transmission, control, and prevention. A public health perspective will be advanced within the assignment.
Click here to read the background information specific for the module 1 SLP THE MODULE 1 OUTBREAK DETECTION (This is included above)
Your Task for this modular component
Please answer these questions
1. What could account for the increase in cases?
2. Compare the DNA fingerprints in Figure 2 from seven of the E. coli O157:H7 cases. Each isolate has its own vertical lane (i.e., column). Controls appear in lanes #1, 5, and 10. Which isolates appear similar? In your opinion was DNA typing necessary in this case? Why?
SLP Assignment Expectations
Length: SLP assignments should be at least 2 pages (500 words) in length.
References: At least two references must be included from academic sources (e.g. peer-reviewed journal articles). Required readings are included. Quoted material should not exceed 10% of the total paper (since the focus of these assignments is critical thinking). Use your own words and build on the ideas of others. When material is copied verbatim from external sources, it MUST be enclosed in quotes. The references should be cited within the text and also listed at the end of the assignment in the References section (APA format recommended).
Organization: Subheadings should be used to organize your paper according to question
Format: APA format is recommended for this assignment. See Syllabus page for more information on APA format.
Grammar and Spelling: While no points are deducted, assignments are expected to adhere to standards guidelines of grammar, spelling, punctuation, and sentence syntax. Points may be deducted if grammar and spelling impact clarity.
The following items will be assessed in particular:
• Achievement of learning objectives for SLP assignment
• Relevance (e.g. all content is connected to the question)
• Precision (e.g. specific question is addressed. Statements, facts, and statistics are specific and accurate).
• Depth of discussion (e.g. present and integrate points that lead to deeper issues)
• Breadth (e.g. multiple perspectives and references, multiple issues/factors considered)
• Evidence (e.g. points are well-supported with facts, statistics and references)
• Logic (e.g. presented discussion makes sense, conclusions are logically supported by premises, statements, or factual information)
• Clarity (e.g. writing is concise, understandable, and contains sufficient detail or examples)
• Objectivity (e.g. avoid use of first person and subjective bias)

Module 2 – Background
MEASURING HEALTH AND DISEASE
Required Readings
Coggon, D., Rose, G., & Barker, D.J.P. (2007) . Quantifying Disease in Populations in Epidemiology for the Uninitiated (4th edition). British Medical Journal. Retrieved on May 22, 2012 from: http://www.bmj.com/about-bmj/resources-readers/publications/epidemiology-uninitiated
Supercourse: Rates, Ratios, and Proportions. (n.d.). Retrieved on May 22, 2012 from: University of Pittsburgh Web site: http://www.pitt.edu/~super1/lecture/lec0441/001.htm
Centers for Disease Control and Prevention. E Coli. Retrieved on May 22, 2012 from: http://www.cdc.gov/ecoli/index.html
A case definition is a standard set of criteria for deciding whether an individual should be classified as having the disease of interest. You may wish to review:
Centers for Disease Control and Prevention. Case Definition E. Coli. Retrieved on May 22, 2012 from: http://wwwn.cdc.gov/NNDSS/script/conditionsummary.aspx?CondID=48
Optional Reading
Shiga Toxin–producing Escherichia coli, New Mexico, USA, 2004–2007. Emerging Infectious Diseases Retrieved on May 22, 2012 from: http://www.cdc.gov/eid/content/15/8/1289.htm
Module 2 – Descriptive Epidemiology and Hypothesis Generation
MEASURING HEALTH AND DISEASE
The incubation period for E. coli O157:H7 ranges from 3-8 days with a median of 3-4 days. The infection often causes severe bloody diarrhea and abdominal cramps, but can also cause a nonbloody diarrhea or result in no symptoms. In some persons, particularly children under 5 years of age and the elderly, the infection can cause a complication called hemolytic uremic syndrome, in which the red blood cells are destroyed and the kidneys fail. About 2-7% of infections lead to this complication.
For this outbreak investigation, a case was defined as diarrhea (at least 3 loose bowel movements a day) and/or abdominal cramps in a resident of the state with onset of symptoms between June 15 and July 15 and a stool culture yielding E.coli O157:H7 with the outbreak strain PFGE pattern.
Of the initial 38 persons who met the case definition, 26 (68%) were female with amedian age of 31 years. (Table 1)
Table1. Age group and gender distribution for persons with E. coli O157:H7 infection and the outbreak PFGE pattern, June 15 – July 15, 1997. (N=38)
Age group (years) Gender TOTAL
Male Female
0-9 2 (17%)* 2 (8%) 4 (11%)
10-19 2 (17%) 3 (12%) 5 (13%)
20-39 3 (25%) 9 (35%) 12 (32%)
40-59 2 (17%) 8 (31%) 10 (26%)
60+ 3 (25%) 4 (15%) 7 (18%)
TOTAL 12 (101%) 26 (101%) 38 (100%)
*percentages refer to column totals.
The 38 cases of E. coli O157:H7 infection meeting the investigation case definition were reported from 10 counties. On set of illness occurred from mid-June to mid-July, peaking on June 22.
From July 16 – 19, hypothesis-generating interviews were undertaken with seven patients. These patients lived in four different counties and ranged in age from 5-69 years. Three of the patients were female.
Hypothesis-generating interviews revealed that most cases had consumed lettuce and alfalfa sprouts in the week before they became ill. No single restaurant or social event was identified in common.
APPENDIX 1. Distribution of E. coli O 157:H7 cases reported to FoodNetSites* by age group and gender, United States, 1997. (N=340)
Age group (years) Gender TOTAL
Male Female
0-<1 5 (3%) 5 (3%) 10 (3%)
1-9 77 (48%) 77 (43%) 154 (45%)
10-19 36 (22%) 18 (10%) 54 (16%)
20-29 10 (6%) 20 (11%) 30 (9%)
30-39 6 (4%) 12 (7%) 18 (5%)
40-49 7 (4%) 5 (3%) 12 (4%)
50-59 7 (4%) 17 (10%) 24 (7%)
60+ 14 (9%) 24 (13%) 38 (11%)
TOTAL 162 (100%) 178 (100%) 340 (100%)
*Foodborne Diseases Active Surveillance Network (FoodNet) is a collaborative project between CDC, the U.S. Department of Agriculture (USDA), the Food and Drug Administration (FDA), and selected state and local health departments. In 1997, FoodNet conducted population based active surveillance for confirmed cases of Campylobacter, Escherichia coli O157, Listeria,Salmonella, Shigella, Vibrio, and Yersinia infectionsin Minnesota, Oregon, and selected counties in California, Connecticut, and Georgia (total population: 16.1 million).
Module 2 – Case
MEASURING HEALTH AND DISEASE
Case Assignment
As part of a State Budget and Appropriations Subcommittee, you have been charged with reviewing health data of local health jurisdictions and establishing priorities for funding for the upcoming fiscal year.
After reviewing the following information
Eagle Rock County San Marino County Baldwin County
Population
2,490,653 299,658 250,765
>65 years 372,166 99,885 2,857
Total Population 2,862,819 399,543 253,622
Number of Deaths
4955 900 1854
>65 yrs 9,845 3,700 455
Total Deaths 14,800 4,600 2,309
Cause of Death
Coronary Heart Disease 6,200 1,800 790
Cancer 3,300 1,000 429
Homicide 3,100 800 450
Motor Vehicle Accident 2,200 1,000 640
Case Assignment
Your task is to answer these questions:
1. Calculate and compare the crude and age-specific death rates for each of the three counties (refer to the information Crude, Specific, and Adjusted Rates in the module homepage). Based on the crude death rate, which county appears to have the greatest need for funding? Does the age-specific death rate change your view regarding which county has a greater need for funding? Explain. Why is it possible to have a low crude rate and higher age-specific death rates?
2. Calculate and compare the cause-specific death rates (Use the information at http://www.pitt.edu/~super1/lecture/lec0441/001.htm from your background readings). For this, combine data from all counties. Based on the data provided, what do you think are the main health priorities?
Assignment Expectations
Length: Case assignments should be at least 2 pages (500 words) in length.
References: At least two references must be included from academic sources (e.g. peer-reviewed journal articles). Required readings are included. Quoted material should not exceed 10% of the total paper (since the focus of these assignments is critical thinking). Use your own words and build on the ideas of others. When material is copied verbatim from external sources, it MUST be enclosed in quotes. The references should be cited within the text and also listed at the end of the assignment in the References section (APA format recommended).
Organization: Subheadings should be used to organize your paper according to question
Format: APA format is recommended for this assignment. See Syllabus page for more information on APA format.
Grammar and Spelling: While no points are deducted, assignments are expected to adhere to standards guidelines of grammar, spelling, punctuation, and sentence syntax. Points may be deducted if grammar and spelling impact clarity.
The following items will be assessed in particular:
• Achievement of learning objectives for case assignment
• Relevance (e.g. all content is connected to the question)
• Precision (e.g. specific question is addressed. Statements, facts, and statistics are specific and accurate).
• Depth of discussion (e.g. present and integrate points that lead to deeper issues)
• Breadth (e.g. multiple perspectives and references, multiple issues/factors considered)
• Evidence (e.g. points are well-supported with facts, statistics and references)
• Logic (e.g. presented discussion makes sense, conclusions are logically supported by premises, statements, or factual information)
• Clarity (e.g. writing is concise, understandable, and contains sufficient detail or examples)
• Objectivity (e.g. avoid use of first person and subjective bias)
Module 2 – SLP
MEASURING HEALTH AND DISEASE
A Multistate Outbreak of E. coli 0157:H7
Click here to read the Module 2 SLP background THE MODULE 2 READING is included above

Session Long Project
Please answer these questions:
1. What are the advantages and disadvantages of the case definition?
2. Describe and compare the age and gender distribution of E. coli O157:H7 cases from this outbreak and those reported from U.S. FoodNet sites in 1997.
3. What kinds of questions would you ask in the hypothesis-generating interviews?
4. Given your knowledge about E. coli O157:H7, the descriptive epidemiology of the initial cases, and the results of hypothesis-generating interviews, outline the information available at this point on the source of the outbreak and mode of transmission
SLP Assignment Expectations
Length: SLP assignments should be at least 2 pages (500 words) in length.
References: At least two references must be included from academic sources (e.g. peer-reviewed journal articles). Required readings are included. Quoted material should not exceed 10% of the total paper (since the focus of these assignments is critical thinking). Use your own words and build on the ideas of others. When material is copied verbatim from external sources, it MUST be enclosed in quotes. The references should be cited within the text and also listed at the end of the assignment in the References section (APA format recommended).
Organization: Subheadings should be used to organize your paper according to question
Format: APA format is recommended for this assignment. See Syllabus page for more information on APA format.
Grammar and Spelling: While no points are deducted, assignments are expected to adhere to standards guidelines of grammar, spelling, punctuation, and sentence syntax. Points may be deducted if grammar and spelling impact clarity.
The following items will be assessed in particular:
• Achievement of learning objectives for SLP assignment
• Relevance (e.g. all content is connected to the question)
• Precision (e.g. specific question is addressed. Statements, facts, and statistics are specific and accurate).
• Depth of discussion (e.g. present and integrate points that lead to deeper issues)
• Breadth (e.g. multiple perspectives and references, multiple issues/factors considered)
• Evidence (e.g. points are well-supported with facts, statistics and references)
• Logic (e.g. presented discussion makes sense, conclusions are logically supported by premises, statements, or factual information)
• Clarity (e.g. writing is concise, understandable, and contains sufficient detail or examples)
• Objectivity (e.g. avoid use of first person and subjective bias)
Module 3 – Background
DESCRIPTIVE AND ANALYTIC EPIDEMIOLOGY
If you cannot locate an article in one set of databases (e.g., EBSCO), try to locate it in ProQuest.
Required Readings
A guide to research methods. Evidence based medicine and study designs at Suny Downstate Medical Center. Retrieved on May 22, 2012 from: http://library.downstate.edu/EBM2/2100.htm
Coggon, D., Rose, G., & Barker, D.J.P. (2007) Case Control and Cross-Sectional studies in Epidemiology for the Uninitiated (4th edition). British Medical Journal. Retrieved on May 22, 2012 from: http://www.bmj.com/about-bmj/resources-readers/publications/epidemiology-uninitiated
Centers for Disease Control and Prevention (2012). Lesson 1: Introduction to Epidemiology, Section 6: Descriptive Epidemiology. In Principles of Epidemiology in Public Health Practice, 3rd Edition. Retrieved March 7, 2013 at http://www.cdc.gov/osels/scientific_edu/ss1978/lesson1/Section6.html
Case Control Studies. Universigty of Pitssburg Supercourse. Retrieved on May 22, 2012 from: http://www.pitt.edu/~super1/lecture/lec8591/index.htm
Optional Readings
Schoenbach, V.J., Rosamond, V.D., Understanding the fundamentals of epidemiology. An evolving text. UNC School of Public Health. Retrieved on May 22, 2012 from: http://www.epidemiolog.net/evolving/TableOfContents.htm
Supercourse: Epidemiologic Design I: Focus on Descriptive Study. Retrieved on May 22, 2012 from: University of Pittsburgh Web site http://www.pitt.edu/~super1/lecture/lec0551/index.htm
Module 3 – Case
DESCRIPTIVE AND ANALYTIC EPIDEMIOLOGY
Case Assignment
Below is epidemiologic data collected on an unknown pathogen.
Your task for this case assignment:
1. Describe these data by person, place, and time (i.e. descriptive epidemiology). For more information on descriptive epidemiology, please refer to the Module 3 Home Page.
2. Provide possible explanations for the pattern of this disease.
Figure 1: Incidence Rate of Unknown Disease by Age and Gender

Figure 2: Geographical Distribution of Unknown Disease in the United States

Figure 3: Incidence Rate of Unknown Disease by State
Figure 4: Frequency of Unknown Disease by Month of Onset

Figure 5: Frequency of Unknown Disease by Year

Assignment Expectations
Length: Case assignments should be at least 3 pages (750 words) in length.
References: At least two references must be included from academic sources (e.g. peer-reviewed journal articles). Required readings are included. Quoted material should not exceed 10% of the total paper (since the focus of these assignments is critical thinking). Use your own words and build on the ideas of others. When material is copied verbatim from external sources, it MUST be enclosed in quotes. The references should be cited within the text and also listed at the end of the assignment in the References section (APA format recommended).
Organization: Subheadings should be used to organize your paper according to question
Format: APA format is recommended for this assignment. See Syllabus page for more information on APA format.
Grammar and Spelling: While no points are deducted, assignments are expected to adhere to standards guidelines of grammar, spelling, punctuation, and sentence syntax. Points may be deducted if grammar and spelling impact clarity.
The following items will be assessed in particular:
• Achievement of learning objectives for case assignment
• Relevance (e.g. all content is connected to the question)
• Precision (e.g. specific question is addressed. Statements, facts, and statistics are specific and accurate).
• Depth of discussion (e.g. present and integrate points that lead to deeper issues)
• Breadth (e.g. multiple perspectives and references, multiple issues/factors considered)
• Evidence (e.g. points are well-supported with facts, statistics and references)
• Logic (e.g. presented discussion makes sense, conclusions are logically supported by premises, statements, or factual information)
• Clarity (e.g. writing is concise, understandable, and contains sufficient detail or examples)
• Objectivity (e.g. avoid use of first person and subjective bias)
Module 3 – SLP
DESCRIPTIVE AND ANALYTIC EPIDEMIOLOGY
Designing an Epidemiologic Study to Test the Hypothesis
To test the hypothesis on the source of the outbreak, a case-control study was conducted from July 21-27. Thirty-one of the initial 38 persons meeting the original case definition (i.e., those not used in hypothesis generating interviews) were included as cases. It was decided that two controls would be selected for every case and would be matched to the case by age group (0-<2 years, 2-<5 years, 5-<12 years, 12-<18 years, 18-<60 years, and 60+ years) and gender.
The investigators identified controls for the study using sequential digit dialing. Exposure information among cases was collected for the 7 days before onset of illness. For controls, exposure information was collected for the 7 days before the interview and for the 7 days before the onset of illness in the matching case.
Twenty-seven case-control sets were interviewed; the remaining case-patients could not be reached.
Session Long Project
Please answer these questions:
1. How would you define controls for this study? What methods might be used to identify controls?
2. Do you agree with the investigators’ decision to match on age group and gender? Why or why not?
3. Over what time period would you examine exposures to possible risk factors for cases? For controls?
SLP Assignment Expectations
Length: SLP assignments should be at least 2 pages (500 words) in length.
References: At least two references must be included from academic sources (e.g. peer-reviewed journal articles). Required readings are included. Quoted material should not exceed 10% of the total paper (since the focus of these assignments is critical thinking). Use your own words and build on the ideas of others. When material is copied verbatim from external sources, it MUST be enclosed in quotes. The references should be cited within the text and also listed at the end of the assignment in the References section (APA format recommended).
Organization: Subheadings should be used to organize your paper according to question
Format: APA format is recommended for this assignment. See Syllabus page for more information on APA format.
Grammar and Spelling: While no points are deducted, assignments are expected to adhere to standards guidelines of grammar, spelling, punctuation, and sentence syntax. Points may be deducted if grammar and spelling impact clarity.
The following items will be assessed in particular:
• Achievement of learning objectives for SLP assignment
• Relevance (e.g. all content is connected to the question)
• Precision (e.g. specific question is addressed. Statements, facts, and statistics are specific and accurate).
• Depth of discussion (e.g. present and integrate points that lead to deeper issues)
• Breadth (e.g. multiple perspectives and references, multiple issues/factors considered)
• Evidence (e.g. points are well-supported with facts, statistics and references)
• Logic (e.g. presented discussion makes sense, conclusions are logically supported by premises, statements, or factual information)
• Clarity (e.g. writing is concise, understandable, and contains sufficient detail or examples)
• Objectivity (e.g. avoid use of first person and subjective bias)
Module 4 – Background
MEASURES OF ASSOCIATION
Required Readings
Centers for Disease Control and Prevention (CDC). (2009) Outbreak of Salmonella serotype Saintpaul infections associated with eating alfalfa sprouts – United States, 2009. MMWR Morb Mortal Wkly,;58(18):500-3. Retrieved on May 22, 2012 from: http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5818a4.htm
Meirik O., Cohort and case control studies. Retrieved May 22, 2012 from: http://www.gfmer.ch/Books/Reproductive_health/Cohort_and_case_control_studies.html
Spitalnic S (2006). Risk Assessment II: Odds Ratio. Hospital Physician, 2006 Jan: 23-26. Retrieved May 22, 2012, from http://www.turner-white.com/memberfile.php?PubCode=hp_jan06_odds.pdf
Redbook: Toxicological Principles for the Safety Assessment of Food Ingredients. U.S. Department of Health and Human Services, Food and Drug Administration, Center for Food Safety and Applied Nutrition July 2000; Updated July 2007. Retrieved May 22, 2012 from http://www.fda.gov/downloads/Food/GuidanceRegulation/UCM222779.pdf
Supercourse, Epidemiology, the Internet and Global health. Different kinds of Epidemiologic Designs. Retrieved May 22, 2012, from University of Pittsburgh Web site http://www.pitt.edu/~super1/lecture/lec0571/index.htm
Supercourse, Epidemiology, the Internet and Global health. Epidemiologic Design II, Focus on Analytic Study Retrieved May 22, 2012, from University of Pittsburgh Web site http://www.pitt.edu/~super1/lecture/lec0561/index.htm
Optional Reading
Redbook: Toxicological Principles for the Safety Assessment of Food Ingredients. U.S. Department of Health and Human Services, Food and Drug Administration, Center for Food Safety and Applied Nutrition July 2000; Updated July 2007. Retrieved May 22, 2012 from http://www.fda.gov/Food/GuidanceComplianceRegulatoryInformation/GuidanceDocuments/
FoodIngredientsandPackaging/Redbook/default
Module 4 – How to calculate an odds ratio
MEASURES OF ASSOCIATION
A2x2 table is used to calculate an odds ratio:
Disease No Disease
Exposed a b
Unexposed c d
The formula for odds ratio is:
Odds ratio = (a xd)/(b x c)
If a researcher selects 50 Lyme disease cases and 100 unmatched controls for a case-control study, and the results indicated that 45 cases and 10 controls recently hiked in a national forest, the odds ratio would be calculated as follows:
Cases Controls Total
Hiking 45 10 55
No Hiking 5 90 95
Total 50 100 150
Odds ratio = (45 x 90) ÷ (10 x 5) = 81
Module 4 – How to calculate a relative risk
MEASURES OF ASSOCIATION
A2x2 table is used to calculate a relative risk:
Disease No Disease
Exposed a b
Unexposed c d
The formula for relative risk is:
Relativerisk = (a/(a+b)) ÷ (c/(c+d))
If 5000 smokers and 5000 non-smokers were selected for a cohort study, and the results of the study indicated that 50 of the 5000 smokers developed lung cancer and 2 of the 5000 non-smokers developed cancer, relative risk would be calculated as follows:
Lung cancer No lung cancer Total
Smokers 50 4950 5000
Non-smokers 2 4998 5000
Total 52 9948 10,000
Relative risk = (50/5000) ÷(2/5000) = 25
Module 4 – Case
MEASURES OF ASSOCIATION
Case Assignment
As an epidemiologist for the County Disease Control Office, you are investigating an outbreak that occurred at a restaurant. The predominant symptoms included vomiting (81%), nausea (76%), and diarrhea (76%). The average incubation period was five hours with an average duration of 19 hours. Items consumed among the ill included prime rib, baked potato with butter, and green salad with dressing.
Figure 1:
FOOD ITEMS PERSONS WHO ATE SPECIFIED FOOD PERSONS WHO DID NOT EAT SPECIFIED FOOD
Ill Not Ill Total Ill Not Ill Total
Prime Rib 18 3 21 3 5 8
Baked Potato 19 4 23 2 4 6
Green Salad 18 9 27 1 1 2
Figure 2:
Food Item 95% Confidence Interval
Prime Rib 1.4 – 65.7
Baked Potato 1.6 -218.5
Green Salad .10 – 42.9
Case Assignment
Your task for this case assignment is to answer these questions:
1. What type of study was used for this investigation? Explain.
2. What would be the appropriate measure of association for this study?
3. Calculate the food-specific attack rates and calculate the measure of association between illness and each food item.
4. What does a confidence interval mean, and which 95% confidence intervals are statistically significant?
5. What do the results indicate regarding the likely source of exposure?
Assignment Expectations
Length: Case assignments should be at least 2 pages (500 words) in length.
References: At least two references must be included from academic sources (e.g. peer-reviewed journal articles). Required readings are included. Quoted material should not exceed 10% of the total paper (since the focus of these assignments is critical thinking). Use your own words and build on the ideas of others. When material is copied verbatim from external sources, it MUST be enclosed in quotes. The references should be cited within the text and also listed at the end of the assignment in the References section (APA format recommended).
Organization: Subheadings should be used to organize your paper according to question
Format: APA format is recommended for this assignment. See Syllabus page for more information on APA format.
Grammar and Spelling: While no points are deducted, assignments are expected to adhere to standards guidelines of grammar, spelling, punctuation, and sentence syntax. Points may be deducted if grammar and spelling impact clarity.
The following items will be assessed in particular:
• Achievement of learning objectives for case assignment
• Relevance (e.g. all content is connected to the question)
• Precision (e.g. specific question is addressed. Statements, facts, and statistics are specific and accurate).
• Depth of discussion (e.g. present and integrate points that lead to deeper issues)
• Breadth (e.g. multiple perspectives and references, multiple issues/factors considered)
• Evidence (e.g. points are well-supported with facts, statistics and references)
• Logic (e.g. presented discussion makes sense, conclusions are logically supported by premises, statements, or factual information)
• Clarity (e.g. writing is concise, understandable, and contains sufficient detail or examples)
• Objectivity (e.g. avoid use of first person and subjective bias)
Module 4 – SLP
MEASURES OF ASSOCIATION
PART IV – Analysis and Interpretation
In the case-control study, the odds ratio for alfalfa sprouts was 29, with the 95% confidence interval 7.5 – 545.2.
Session Long Project
Answer these questions
1. Is this odds ratio statistically significant? Please explain.
2. Do you think there is a causal relationship between exposure (eating alfalfa sprouts) and disease? Please explain (using the applicable criteria under “Does Association Mean Causality” in your modular homepage)
SLP Assignment Expectations
Length: SLP assignments should be at least 2 pages (500 words) in length.
References: At least two references must be included from academic sources (e.g. peer-reviewed journal articles). Required readings are included. Quoted material should not exceed 10% of the total paper (since the focus of these assignments is critical thinking). Use your own words and build on the ideas of others. When material is copied verbatim from external sources, it MUST be enclosed in quotes. The references should be cited within the text and also listed at the end of the assignment in the References section (APA format recommended).
Organization: Subheadings should be used to organize your paper according to question
Format: APA format is recommended for this assignment. See Syllabus page for more information on APA format.
Grammar and Spelling: While no points are deducted, assignments are expected to adhere to standards guidelines of grammar, spelling, punctuation, and sentence syntax. Points may be deducted if grammar and spelling impact clarity.
The following items will be assessed in particular:
• Achievement of learning objectives for SLP assignment
• Relevance (e.g. all content is connected to the question)
• Precision (e.g. specific question is addressed. Statements, facts, and statistics are specific and accurate).
• Depth of discussion (e.g. present and integrate points that lead to deeper issues)
• Breadth (e.g. multiple perspectives and references, multiple issues/factors considered)
• Evidence (e.g. points are well-supported with facts, statistics and references)
• Logic (e.g. presented discussion makes sense, conclusions are logically supported by premises, statements, or factual information)
• Clarity (e.g. writing is concise, understandable, and contains sufficient detail or examples)
• Objectivity (e.g. avoid use of first person and subjective bias)
Module 5 – Background
SCREENING FOR DISEASES
Required Readings
Loong, TZ (2003). Understanding sensitivity and specificity with the right side of the brain.
British Medical Journal (International edition), 327, 716-720. Retrieved on May 22, 2012 from ProQuest. This is the attachment.

Dechet A (2005). Foodborne Illness Outbreaks and Sprouts. FDA Public Meeting: 2005 Sprout Safety. Centers for Disease Control and Prevention. Retrieved May 22, 2012 from www.fda.gov/ohrms/dockets/dockets/05n0147/05n-0147-ts00001-dechet.ppt
Supercourse, Epidemiology, the Internet and Global health. Screening and Disease Prevention. Retrieved May 22, 2012 from University of Pittsburgh Web site Screening and Disease Prevention. (n.d.). http://www.pitt.edu/~super1/lecture/lec0721/index.htm
PATH (2008). Accuracy of Diagnostic Tests. Retrieved May 22, 2012 from http://sites.path.org/dx/rapid-dx/performance/

University of Washington (nd). Epidemiology Glossary ; Retrieved May 22, 2012 from http://depts.washington.edu/physdx/eglossary.html
Lalkhen, AG and McCluskey, A (2008). Clinical tests: sensitivity and specificity. Contin Educ Anaesth Crit Care Pain; 8(6): 221-223 doi:10.1093/bjaceaccp/mkn041. Retrieved March 7, 2013 at http://ceaccp.oxfordjournals.org/content/8/6/221.full
For the SLP
While the assignment may be based on a real case, the questions can refer to any outbreak that involved sprouts and E. coli 0157:H7. Knowing the specific pathogen (its characteristics, transmission) and the specific food, how could have the contamination occurred? You are asked to think about a possible point of contamination and about measures of control. Here is another potentially useful reference:
World Health Organization (2011). Enterohaemorrhagic Escherichia coli (EHEC). Retrieved May 22, 2012 from http://www.who.int/mediacentre/factsheets/fs125/en/
Optional Reading
Gray RH, Makumbi F, Serwadda D, et. al. (2006) Limitations of rapid HIV-1 tests during screening for trials in Uganda: diagnostic test accuracy study. BMJ, 335(7612):188. Retrieved on May 22, 2012 from http://www.bmj.com/highwire/filestream/378714/field_highwire_article_pdf/0.pdf
Module 5 – SLP Background
SCREENING FOR DISEASES
PART V – Other Investigations
Tracebacks of food are often necessary to identify sources of contamination and quickly limit a public health threat by removing these sources. One purpose of a traceback is to ascertain the distribution and production chain for a food product so that an effective recall can be undertaken. Tracebacks can also clarify the point or points at which the implicated food was likely to have become contaminated and help determine how to prevent similar outbreaks in the future. Epidemiologic tracebacks can accomplish each of these goals, but are different from the more detailed, regulatory tracebacks which follow rules of legal evidence.
An epidemiologic traceback usually begins with the information available at the time of purchase of the implicated food item and extends back to the very beginning of its production. All production steps, from harvest to consumption, are examined.
Full tracebacks leading to formal product recalls can be time-consuming and result in many dead-ends. Pertinent information and records are often missing or poorly maintained. Traceback efforts may require hundreds of hours of tedious work and may extend to other states and countries.
MDCH and CDC decided to do an epidemiologic traceback of the alfalfa sprouts implicated in the Michigan outbreak.
Of the 16 patients who ate sprouts for whom the source of the sprouts could be traced, 15 led to a single sprouting facility, facility A in Michigan; in the remaining traceback, the patient could have eaten sprouts from either facility A or facility B in Michigan. (Figure 4) Facility A and B were the only facilities that sprouted alfalfa seed in the state. Sprouts grown by facility A at the time of the outbreak came from two lots of seed: one from Idaho and one from Australia.
At this point, the investigators became aware of a concurrent outbreak of E.coli O157:H7 infection in Virginia. CDC subtyped the strains from Virginia and identified the same PFGE pattern as in the Michigan outbreak. A case-control study conducted by the Virginia Department of Health (VDH) linked the concurrent outbreak of O157:H7 infections to alfalfa sprouts.
In Virginia, the source of sprouts could be traced for 13 patients; all led to one sprouting company in Virginia. (Figure 4) The Virginia sprouting company was using a single lot of seed harvested in Idaho –the same lot as the one used at facility A in Michigan. Traceback of the seed to the distributor identified it as part of a17,000 pound lot of which 6,000 pounds still remained.
Figure 4. Traceback results of the E.coli O157:H7 investigation of alfalfa sprouts in Michigan (MI) and Virginia(VA), 1997.
The implicated seed lot was a blend of 5 lots from fields of four farmers and was harvested between 1984 and 1996. The seed processor and the farmers were located in Idaho.
Inspection of the alfalfa fields revealed three possible sources of contamination: cattle manure, irrigation water, and deer feces. Although manure is not normally applied to alfalfa fields in Idaho, cattle feed lots were common in this area and the alfalfa fields of one farmer were adjacent to a feed lot. Manure may have leaked or been illegally dumped onto the alfalfa fields or run-off water from neighboring fields, contaminated by manure, may have been used to irrigate the alfalfa fields. In addition, three of four farmers occasionally saw deer in their fields and one field was situated next to a wildlife refuge.
The seed from each of the farmers was harvested and mechanically cleaned at the same seed processing plant. The seeds were then placed in 50 lb. bags. No further processing occurred. Most of the seed was produced to plant alfalfa fields (e.g., to produce hay for livestock feed); the relatively small amount of seed used for sprouting was not handled any differently than the raw agricultural commodity seed.
Note:*A 1988 outbreak of Salmonella Saint Paul infections in Europe was linked to mung bean sprouts. A small 1990 cluster of Salmonella Anatum infections in the United States was suspected to be linked to one grower’s alfalfa sprouts, but the source of contamination was not determined. A 1994 Salmonella Bovismorbificans outbreak in Finland and Sweden was traced to Australian alfalfa seed. In 1995, it was concluded that sprouts caused an international outbreak of Salmonella Stanley, affecting persons in more than 17 states in the United States and Finland. In that same year, another multinational outbreak of salmonellosis (due to S. entericaserotype Newp01ort) was linked to alfalfa seeds after an increase in infections was detected in Oregon and British Columbia. In 1996, almost 10,000 cases of E. coli O157:H7 occurred among school children in Japan. The outbreak was ultimately shown to be caused by radish sprouts grown from seed imported from the U.S.
Part VI Control
The implicated seed lot was not distributed to any other sprouting companies in or outside the United States. The remaining 6,000 lbs. of seed was immediately removed from the marketplace. A sample of 500 grams of seed was cultured directly, and the same amount was sprouted and then cultured; neither yielded E. coli O157:H7.
The Idaho Division of Food and Drugs held meetings at which public health officials explained to seed growers the need to protect alfalfa and other seeds used in sprouting from contamination during growing, harvesting, and packing. Both MDCH and the VDH made public television and radio announcements about the risk of contaminated sprouting seeds and recommended that persons at high risk for complications from E. coli O157:H7 infection not eat sprouts.
The Center for Food Safety and Quality Enhancement began working with the sprout industry to identify ways to make sprouts safer for human consumption. In tests with artificially inoculated seed, treating the seed by soaking it in a chlorine solution* (2000 ppm hypochlorite in 57-60EC water) at the time of sprouting reduced the level of contamination by a thousand-fold. Irradiation has also been tested and appears to work well in decontaminating sprout seeds. However, this treatment leads to diminished sprouting ability and has not been approved by the FDA.
*Chemical treatment with a hypochlorite solution is a U.S. Food and Drug Administration (FDA) approved treatment of foods.
Module 5 – Case
SCREENING FOR DISEASES
Assignment Overview
Infection with the human immunodeficiency virus (HIV) is routinely diagnosed by detecting the presence of specific antibodies in the patient’s serum. Although the presence of the virus itself can be now be detected (i.e. polymerase chain reaction [PCR] to measure plasma HIV RNA, or “viral load”), these tests remain expensive and require laboratory techniques that are not routinely available. The diagnosis of HIV infection begins with an enzyme immunoassay (EIA). The optical density (OD) of the patient’s EIA is compared to a control specimen (OD ratio). If the OD ratio is – above the established cutoff for that control sample on repeat testing the specimen is termed “repeatedly reactive”. The EIA is relatively sensitive, fast, simple and inexpensive which makes it an appropriate screening test. However, if one examines the ODs for a large group of samples from patients with and without true HIV infection you can see that there is some overlap in their EIA results if a value of A is used for the cutoff:

Hypothetical distribution of OD ratios for patients with and without HIV infection.
Hypothetical distribution of OD ratios for patients with and without HIV infection.
Patients with HIV infection are depicted with blue, thick line,those without HlV with red, thin line.
Where a cutoff is drawn to determine a diagnostic test result may be somewhat arbitrary.
Case Assignment
Answer these questions:
1. What would be the impact on this test’s sensitivity if you moved the cutoff for a positive result from A to B? What about specificity? What would happen to sensitivity and specificity if you moved the cutoff from A to C? Where would you put the cutoff for this test? What is the relationship between sensitivity and specificity for any given test?
2. Where would the director of the Blood Bank who is screening donated blood for HIV antibody want to put the cutoff? What would be the potential problem caused by this decision? Where would an investigator enrolling high-risk patients in a clinical trial for an experimental, potentially toxic antiretroviral draw the cutoff? What would be the potential problem caused by this decision? In your answer please detail possible ethical and legal issues of possible concern.
Assignment Expectations
Length: Case assignments should be at least 2 pages (500 words) in length.
References: At least two references must be included from academic sources (e.g. peer-reviewed journal articles). Required readings are included. Quoted material should not exceed 10% of the total paper (since the focus of these assignments is critical thinking). Use your own words and build on the ideas of others. When material is copied verbatim from external sources, it MUST be enclosed in quotes. The references should be cited within the text and also listed at the end of the assignment in the References section (APA format recommended).
Organization: Subheadings should be used to organize your paper according to question
Format: APA format is recommended for this assignment. See Syllabus page for more information on APA format.
Grammar and Spelling: While no points are deducted, assignments are expected to adhere to standards guidelines of grammar, spelling, punctuation, and sentence syntax. Points may be deducted if grammar and spelling impact clarity.
The following items will be assessed in particular:
• Achievement of learning objectives for case assignment
• Relevance (e.g. all content is connected to the question)
• Precision (e.g. specific question is addressed. Statements, facts, and statistics are specific and accurate).
• Depth of discussion (e.g. present and integrate points that lead to deeper issues)
• Breadth (e.g. multiple perspectives and references, multiple issues/factors considered)
• Evidence (e.g. points are well-supported with facts, statistics and references)
• Logic (e.g. presented discussion makes sense, conclusions are logically supported by premises, statements, or factual information)
• Clarity (e.g. writing is concise, understandable, and contains sufficient detail or examples)
• Objectivity (e.g. avoid use of first person and subjective bias)

Module 5 – SLP
SCREENING FOR DISEASES
Please answer the questions
1. Knowing the pathogen and its characteristics (including modes of transmission) where do you think was the most likely point of contamination in the production of the sprouts? In inspecting the alfalfa fields and harvesting process, what possible points of contamination should be considered?
2. What interventions/control measures would you suggest? Why?
3. In preparing a report of this investigation what possible strengths and limitations should be discussed?”
SLP Assignment Expectations
Length: SLP assignments should be at least 2 pages (500 words) in length.
References: At least two references must be included from academic sources (e.g. peer-reviewed journal articles). Required readings are included. Quoted material should not exceed 10% of the total paper (since the focus of these assignments is critical thinking). Use your own words and build on the ideas of others. When material is copied verbatim from external sources, it MUST be enclosed in quotes. The references should be cited within the text and also listed at the end of the assignment in the References section (APA format recommended).
Organization: Subheadings should be used to organize your paper according to question
Format: APA format is recommended for this assignment. See Syllabus page for more information on APA format.
Grammar and Spelling: While no points are deducted, assignments are expected to adhere to standards guidelines of grammar, spelling, punctuation, and sentence syntax. Points may be deducted if grammar and spelling impact clarity.
The following items will be assessed in particular:
• Achievement of learning objectives for SLP assignment
• Relevance (e.g. all content is connected to the question)
• Precision (e.g. specific question is addressed. Statements, facts, and statistics are specific and accurate).
• Depth of discussion (e.g. present and integrate points that lead to deeper issues)
• Breadth (e.g. multiple perspectives and references, multiple issues/factors considered)
• Evidence (e.g. points are well-supported with facts, statistics and references)
• Logic (e.g. presented discussion makes sense, conclusions are logically supported by premises, statements, or factual information)
• Clarity (e.g. writing is concise, understandable, and contains sufficient detail or examples)
• Objectivity (e.g. avoid use of first person and subjective bias)
Answer questions separately in a paragraph each with a cited source for each
1 Explain the importance of epidemiology for informing scientific, ethical, economic and political discussion of health issues.

2 Please choose an infectious disease (e.g. TB) and list which disease you have chosen. Then, please identify key sources of data that can be used to detect and control this disease in non-endemic countries. In your view are these sources of data sufficient?

3 Descriptive epidemiology involves examining the patterns of disease by person, place, and time. Descriptive epidemiology may also be used to distinguish a natural outbreak from an intentional outbreak (i.e. bioterrorism). In the American Anthrax Outbreak of 2001 (http://www.ph.ucla.edu/epi/bioter/detect/antdetect_intro.html), what were the initial epidemiologic clues that indicated that the outbreak may have been intentional?

4 Foodborne disease is a significant problem as discussed in this article: http://wwwnc.cdc.gov/eid/article/3/4/97-0414_article.htm According to this article, what are some of the factors contributing to this problem and what strategies would you propose to address this problem?

5 One of the problems in medicine and epidemiology today is the emergence of superbugs or multi-resistant bacteria. What are some of the factors that have contributed to antibiotic resistance? What strategies would you propose to address this problem?
CDC (2011) Antimicrobial Resistance Posing Growing Health Threat. Retrieved from http://www.cdc.gov/media/releases/2011/p0407_antimicrobialresistance.html
Optional reading:
CDC (2010) Antibiotic Resistance and the Threat to Public Health, Statement of Thomas Frieden, M.D., M.P.H. before Committee on Energy and Commerce Subcommittee on Health United States House of Representatives. Retrieved from ttp://www.cdc.gov/drugresistance/pdf/FriedenTestimony42810.pdf

Module 1 – Background
INTRODUCTION TO EPIDEMIOLOGY: THE EPIDEMIOLOGIC APPROACH
Required Readings
Coggon, D., Rose, G., & Barker, D.J.P. (2007) Epidemiology for the Uninitiated (4th edition). British Medical Journal. Retrieved May 22, 2012 from http://www.bmj.com/about-bmj/resources-readers/publications/epidemiology-uninitiated
Centers for Disease Control and Prevention. PulseNet. Retrieved Retrieved May 22, 2012 from http://www.cdc.gov/pulsenet/
Centers for Disease Control and Prevention Timeline for Reporting of E. coli Cases. Retrieved February 26, 2011. http://www.cdc.gov/ecoli/reportingtimeline.htm
OMRAN, A. (2005). The Epidemiologic Transition: A Theory of the Epidemiology of Population Change. Milbank Quarterly, 83(4), 731-757. doi:10.1111/j.1468-0009.2005.00398.x. Retrieved Retrieved May 22, 2012 from: http://onlinelibrary.wiley.com/doi/10.1111/j.1468-0009.2005.00398.x/pdf
Principles of Epidemiology. Retrieved Retrieved May 22, 2012 from University of Illinois at Chicago Web site: http://www.uic.edu/sph/prepare/courses/ph490/resources/epilesson01.pdf
DNA Fingerprinting. Retrieved May 22, 2012 from cphp.sph.unc.edu/focus/vol4/issue4/4-4LabTechniques_slides.ppt
Module 1 – Multiple causation
INTRODUCTION TO EPIDEMIOLOGY: THE EPIDEMIOLOGIC APPROACH
Multiple causation refers to the prerequisite that more than one factor must be present for disease to develop in a host. When a factor must be present for a disease to occur, it is called the agent of that disease. For example, HIV virus is the agent of AIDS. Although an agent is necessary, it is not sufficient to cause disease. Factors that may affect the development of disease can be classified into two groups:1) host factors and 2) environmental factors.
Host Factors
The state of the host is affected by genetic factors and past environmental exposures. These factors can affect the susceptibility of a host. For example, sickle celltrait (a genetic factor) is associated with a decreased risk of malaria. Past environmental exposures that affect susceptibility include specificimmunity, which is a state of altered responsiveness to a specific substance acquired through immunization or natural infection. Other environmental exposures be chemical in nature (e.g. cigarette smoking, asbestos).
Environmental Factors
Environmental factors can be categorized as biological, social, or physical. Biological factors include the agent of the disease, the place where the agent lives and multiplies (e.g.human beings, animals, soil), vectors that transmit disease (e.g. flies andmosquitoes), and antibiotics. Social factors include the technical level of medical care, health codes controlling environmental hazards, and social customs. For example, the custom of serving chicken tataki (undercooked chicken) may expose an individual to infectious agents, such as Salmonellaor Campylobacter. Physical factorsinclude heat, light, air, water, radiation, gravity, atmospheric pressure, andchemical agents. When weather conditions cause masses of air pollution to be trapped for several days, inhabitants can be exposed to noxious substancesthat can lead to chronic diseases.
Ecologic Models
Ecological models have been developed to illustrate the ways in which these interactions influence the occurrence of disease. Two commonly used models include the epidemiologic triangle and the web of causation.
The epidemiologic triangle consists of three components: host, environment, and agent. A change in any of the components will affect the equilibrium by increasing or decreasing the frequency of disease. For example, individuals exposed to the “common cold” virus may not all become ill because of differences in nutrition or stress (host factors).
The web of causation is often used to explain conditions that have not been linked to specific agents. In this model, more emphasis is placed on the multiplicity of interactions between the host and environment, rather than the agent. According to this model, conditions develop as a result of chains of causation in which each link represent a complex web of antecedents.
Module 1 – Outbreak Detection
INTRODUCTION TO EPIDEMIOLOGY: THE EPIDEMIOLOGIC APPROACH
Escherichia coli O157:H7 was first identified as a human pathogen in 1982 in the United States of America, following an outbreak of bloody diarrhea associated with contaminated hamburger meat. Sporadic infections and outbreaks have since been reported from many parts of the world,including North America, Western Europe, Australia, Asia, and Africa. Although other animals are capable of carrying and transmitting theinfection, cattle are the primary reservoir for E. coli O157:H7. Implicated foods are typically those derived from cattle (e.g., beef,hamburger, raw milk); however, the infection has also been transmitted through contact with infected persons, contaminated water, and other contaminated food products.
Infection with E. coli O157:H7 is diagnosed by detecting the bacterium in the stool. Most laboratories that culture stool do not routinely test for E. coli O157:H7, but require a special request from the health care provider. Only recently has E. coli O157:H7 infection become nationally notifiable in the U.S. Outside the U.S., reporting is limited to a few but increasing number of countries.
In the last week of June 1997, a certain state department of community health in the US noticed an increase in laboratory reports of E. coli O157:H7 infection. Fifty-two infections had been reported that month, compared with 18 in June of 1996. In preliminary investigations, no obvious epidemiologic linkages between the patients were found. The increase in cases continued into July.
Laboratory subtyping can help determine if an increased number of isolates of the same bacterial species results from a common source outbreak. Subtyping methods are based on selected biologic and/or geneticcharacteristics of bacteria that tend to differ between isolates of the same species. In a common source outbreak, however, isolates typically arise from the same parent organism. These isolates will be similar to each other with respect to these biologic and genetic characteristics and have similar subtyping results.
One subtyping method is DNA “fingerprinting” by Pulsed Field Gel Electrophoresis (PFGE). In DNA fingerprinting, the bacterial DNA is cut into pieces. The pieces are separated by placing them in a jelly-like substance (i.e., the gel), acting as a sieve, to which a pulsing electric fieldis applied. The electric field drives the DNA pieces across the gel over a period of hours. The smaller pieces move through the gel more quickly and the larger pieces more slowly resulting in a separation of the DNA into distinct bands. The bands are made to fluoresce and are read under ultraviolet illumination. This DNA“fingerprint” resembles a bar code. (Figure 1)

Figure 1. Typical DNA banding pattern resulting from PFGE.
Different DNA composition will result in different PFGE banding patterns. Bacteria descended from the same original parent will have virtually identical DNA and their DNA fingerprints will be in distinguishable. Identification of a cluster of isolates with the same PFGE pattern suggests that they arose from the same parent and could be from the same source.
Similar DNA fingerprints alone, however, are insufficient to establish a linkage between isolates and a common source outbreak. An epidemiologic investigation is necessary to demonstrate that there is a common source and to identify it. To be most useful, PFGE subtyping needs to be performed on a routine basis, in realtime, so that results are available (and reviewed) soon after a case is first detected.
Figure2. PFGE results on E. coli O157:H7 isolates, June-July 1997.

Typically, a PFGE “pattern” is defined as having the same banding pattern but including up to one band difference. By this definition, isolates #2, 3, 4, 6, and 7 are indistinguishable by these PFGE results. (Isolate #4 differs by one band.)
DNA finger printing, performed during the second week of July showed that 17 of the first 19 E. coli O157:H7 isolates from June-July were indistinguishable. They did not match any fingerprints from a convenience sample of isolates frompatients with E. coli O157:H7 infection before May.
Based on the PFGE findings, it was suspected the cases of E. coli O157:H7 infection resulted from a common source. On July 15, an investigation was initiated.
Module 1 – Natural History of Disease
INTRODUCTION TO EPIDEMIOLOGY: THE EPIDEMIOLOGIC APPROACH
Natural History refers to the course of disease over time, unaffected by treatment. Each disease has its own natural history, which occurs through a sequence of stages:
Stage of Susceptibility
During this stage,the disease has not developed, but the presence of risk factors favor its occurrence. For example, high serum cholesterol levels increase the probability of coronary heart disease and would therefore be considered a risk factor.
Stage of Presymptomatic Disease
Duringthis stage, the disease process has begun, but there are no detectablesymptoms. For example, atherosclerosis (hardening of the arteries) occurring before any signs of disease would be considered presymptomatic disease.
Stage of Clinical Disease
Recognizable symptoms occur during this stage of disease. This stage is often subdivided further for better case management and epidemiologic studies.
Stage of Disability
Some diseases resolve completely and do not reach this stage. However, there are a number of conditions that leave a person temporarily or permanently disabled. For example, stroke can lead to paralysis.
Levels of Prevention
Preventing the natural history of a disease from occurring is an important objective inpublic health. The levels of prevention include:
Primary Prevention
This level of prevention refers to altering susceptibility or reducing exposure tosusceptible individuals (during the stage of susceptibility). Primary prevention includes general health promotion (e.g. good nutrition, adequate rest, sex education) and specific protective measures (e.g.immunization, environmental sanitation).
Secondary Prevention
This level of prevention refers to early detection and treatment of disease (during the pre-symptomatic and clinical stage) . At this prevention level, it is sometimes possible to either cure disease or slow its progression, prevent complications, limit disability, and prevent transmission of infectious disease.
Tertiary Prevention
This level of prevention refers to the alleviation of disability resulting from disease and attempts to restore effective functioning (during the disability stage).
Module 1 – Mechanisms Of Disease Transmission
INTRODUCTION TO EPIDEMIOLOGY: THE EPIDEMIOLOGIC APPROACH
The method by which an infectious agent escapes a reservoir and enters a host is referred to as mechanism of transmission. There are two main types of transmission: direct transmission and indirect transmission. In direct transmission, an infectious agent is immediately transferred from one infected host or reservoir to another. Direct transmission includes not only direct contact, such as kissing, but also spray by droplets through sneezing and coughing onto the mucous membranes of others. Droplet spread is classified as direct transmission because it occurs over short distances–the droplets travel a few feet before falling to the ground.
There are three types of indirect transmission: vehicleborne, vectorborne, and airborne. Vehicleborne transmissionis indirect contact through inanimate objects, such as bedding, toys, surgical instruments, and contaminated food. In vectorborne transmission,the infectious agent is transmitted by an intermediary (usually an insect) to a susceptible host. In airborne transmission, two types of particles may be spread through the air–dusts and droplet nuclei. Dusts are particles of varying size that result from resuspension of particles that have settled on floors or bedding as well as particles blown by the wind.
Coccidioidomycosis is an example of a disease that is spread by airborne transmission of fungal spores. Droplet nuclei are very tiny particles that may be suspended in the air for long periods of time. They represent the dried residue of droplets from coughing, sneezing, or the aerosolization of infective materials.
Infectivity
Infectivity is defined as the ability of the agent to invade and multiply (produce infection in a host). An example of a disease with high infectivity would be measles; a disease with low infectivity would be leprosy. Techniques for evaluating infectivity include speed that an agent spreads through a population and proportion of close contacts who become infected.
Immunity
Immunogenicity is defined as the infection’s ability to produce specific immunity. Immunogenicity can be affected by host factors such as age, nutrition, dose, and virulence of infection.
Herd immunity is defined as the resistance of a group to invasion and spread of an infectious agent, based on the immunity of a high proportion of individual members of the group. Herd immunity is believed to be an important factor in the dynamics of propagated epidemics. Factors that are conducive to the development of large-scale person-to-person epidemics include the introduction of an agent to a population that has never been exposed previously and a large number of susceptible individuals with close contact(e.g. prisons, convalescent homes).
Incubation Period
The time interval between the exposure of an agent and the onset of illness is referred to as the incubation period. During epidemics of unknown pathogens, the incubation period is frequently used to rule out the likely etiologic agent.
Module 1 – Reservoirs
INTRODUCTION TO EPIDEMIOLOGY: THE EPIDEMIOLOGIC APPROACH
Reservoirs are defined as the living organisms or inanimate matter (e.g. soil) where an infectious agent lives and multiplies. The concept of the reservoir is important in infectious disease because the reservoir is the component of the cycle where an infectious agent can survive indefinitely. Humans are the main reservoir for most of the viral and bacterial respiratory diseases. Vertebrate animals are reservoirs for diseases such as brucellosis (from cows, pigs, and goats), anthrax (from sheep), leptospirosis (from rodents), and rabies (from dogs, bats, and other animals). These diseases that are acquired from animals are known as zoonoses.
Module 1 – Variations in Severity
INTRODUCTION TO EPIDEMIOLOGY: THE EPIDEMIOLOGIC APPROACH
An infectious disease may havea wide variety of clinical symptoms, ranging from no symptoms to severe clinical illness or death. Diseases such as tuberculosis have a high proportion of asymptomatic individuals (referred to a slow pathogenicity), while diseases such as measles have a high proportion of symptomatic infections and a small percent of severe or fatal illness. Diseases such as the African hemorrhagic fevers caused by Marburg and Ebolavirus are very severe and usually fatal. For diseases with low pathogenicity, only a small fraction of cases are often diagnosed and reported.
Module 1 – Case
INTRODUCTION TO EPIDEMIOLOGY: THE EPIDEMIOLOGIC APPROACH
Case Assignment
Your task for this case assignment:
Using the materials in the module homepage and in the background section, please address the following:
1. Define and describe the field of Epidemiology (1/2 page)
2. Define and explain epidemiologic transition and describe the factors involved in epidemiologic transition (1 page)
3. Say we suspect a relationship between a specific dietary factor and heart disease. Can you think of ways of epidemiologically assessing whether indeed the dietary factor is a determinant of heart disease? (1/2 page)
4. Which types of diseases do you think pose a greater risk for the population of the United States: infectious diseases or chronic diseases. Please explain (1/2-1 page)
Assignment Expectations
Length: Case assignments should be at least 3 pages (750 words) in length.
References: At least two references must be included from academic sources (e.g. peer-reviewed journal articles). Required readings are included. Quoted material should not exceed 10% of the total paper (since the focus of these assignments is critical thinking). Use your own words and build on the ideas of others. When material is copied verbatim from external sources, it MUST be enclosed in quotes. The references should be cited within the text and also listed at the end of the assignment in the References section (APA format recommended).
Organization: Subheadings should be used to organize your paper according to question
Format: APA format is recommended for this assignment. See Syllabus page for more information on APA format.
Grammar and Spelling: While no points are deducted, assignments are expected to adhere to standards guidelines of grammar, spelling, punctuation, and sentence syntax. Points may be deducted if grammar and spelling impact clarity.
The following items will be assessed in particular:
• Achievement of learning objectives for case assignment
• Relevance (e.g. all content is connected to the question)
• Precision (e.g. specific question is addressed. Statements, facts, and statistics are specific and accurate).
• Depth of discussion (e.g. present and integrate points that lead to deeper issues)
• Breadth (e.g. multiple perspectives and references, multiple issues/factors considered)
• Evidence (e.g. points are well-supported with facts, statistics and references)
• Logic (e.g. presented discussion makes sense, conclusions are logically supported by premises, statements, or factual information)
• Clarity (e.g. writing is concise, understandable, and contains sufficient detail or examples)
• Objectivity (e.g. avoid use of first person and subjective bias)

Module 1 – SLP
INTRODUCTION TO EPIDEMIOLOGY: THE EPIDEMIOLOGIC APPROACH
A Multistate Outbreak of E. coli 0157:H7
For your session-long project, you will conduct an epidemiologic investigation of an outbreak of E. coli 0157:H7. The grade for the SLP is based on the depth of your work and your ability to analyze the information, generate hypotheses about the source of the outbreak and mode of transmission. This means that the student is focusing on those factors of importance to disease transmission, control, and prevention. A public health perspective will be advanced within the assignment.
Click here to read the background information specific for the module 1 SLP THE MODULE 1 OUTBREAK DETECTION (This is included above)
Your Task for this modular component
Please answer these questions
1. What could account for the increase in cases?
2. Compare the DNA fingerprints in Figure 2 from seven of the E. coli O157:H7 cases. Each isolate has its own vertical lane (i.e., column). Controls appear in lanes #1, 5, and 10. Which isolates appear similar? In your opinion was DNA typing necessary in this case? Why?
SLP Assignment Expectations
Length: SLP assignments should be at least 2 pages (500 words) in length.
References: At least two references must be included from academic sources (e.g. peer-reviewed journal articles). Required readings are included. Quoted material should not exceed 10% of the total paper (since the focus of these assignments is critical thinking). Use your own words and build on the ideas of others. When material is copied verbatim from external sources, it MUST be enclosed in quotes. The references should be cited within the text and also listed at the end of the assignment in the References section (APA format recommended).
Organization: Subheadings should be used to organize your paper according to question
Format: APA format is recommended for this assignment. See Syllabus page for more information on APA format.
Grammar and Spelling: While no points are deducted, assignments are expected to adhere to standards guidelines of grammar, spelling, punctuation, and sentence syntax. Points may be deducted if grammar and spelling impact clarity.
The following items will be assessed in particular:
• Achievement of learning objectives for SLP assignment
• Relevance (e.g. all content is connected to the question)
• Precision (e.g. specific question is addressed. Statements, facts, and statistics are specific and accurate).
• Depth of discussion (e.g. present and integrate points that lead to deeper issues)
• Breadth (e.g. multiple perspectives and references, multiple issues/factors considered)
• Evidence (e.g. points are well-supported with facts, statistics and references)
• Logic (e.g. presented discussion makes sense, conclusions are logically supported by premises, statements, or factual information)
• Clarity (e.g. writing is concise, understandable, and contains sufficient detail or examples)
• Objectivity (e.g. avoid use of first person and subjective bias)

Module 2 – Background
MEASURING HEALTH AND DISEASE
Required Readings
Coggon, D., Rose, G., & Barker, D.J.P. (2007) . Quantifying Disease in Populations in Epidemiology for the Uninitiated (4th edition). British Medical Journal. Retrieved on May 22, 2012 from: http://www.bmj.com/about-bmj/resources-readers/publications/epidemiology-uninitiated
Supercourse: Rates, Ratios, and Proportions. (n.d.). Retrieved on May 22, 2012 from: University of Pittsburgh Web site: http://www.pitt.edu/~super1/lecture/lec0441/001.htm
Centers for Disease Control and Prevention. E Coli. Retrieved on May 22, 2012 from: http://www.cdc.gov/ecoli/index.html
A case definition is a standard set of criteria for deciding whether an individual should be classified as having the disease of interest. You may wish to review:
Centers for Disease Control and Prevention. Case Definition E. Coli. Retrieved on May 22, 2012 from: http://wwwn.cdc.gov/NNDSS/script/conditionsummary.aspx?CondID=48
Optional Reading
Shiga Toxin–producing Escherichia coli, New Mexico, USA, 2004–2007. Emerging Infectious Diseases Retrieved on May 22, 2012 from: http://www.cdc.gov/eid/content/15/8/1289.htm
Module 2 – Descriptive Epidemiology and Hypothesis Generation
MEASURING HEALTH AND DISEASE
The incubation period for E. coli O157:H7 ranges from 3-8 days with a median of 3-4 days. The infection often causes severe bloody diarrhea and abdominal cramps, but can also cause a nonbloody diarrhea or result in no symptoms. In some persons, particularly children under 5 years of age and the elderly, the infection can cause a complication called hemolytic uremic syndrome, in which the red blood cells are destroyed and the kidneys fail. About 2-7% of infections lead to this complication.
For this outbreak investigation, a case was defined as diarrhea (at least 3 loose bowel movements a day) and/or abdominal cramps in a resident of the state with onset of symptoms between June 15 and July 15 and a stool culture yielding E.coli O157:H7 with the outbreak strain PFGE pattern.
Of the initial 38 persons who met the case definition, 26 (68%) were female with amedian age of 31 years. (Table 1)
Table1. Age group and gender distribution for persons with E. coli O157:H7 infection and the outbreak PFGE pattern, June 15 – July 15, 1997. (N=38)
Age group (years) Gender TOTAL
Male Female
0-9 2 (17%)* 2 (8%) 4 (11%)
10-19 2 (17%) 3 (12%) 5 (13%)
20-39 3 (25%) 9 (35%) 12 (32%)
40-59 2 (17%) 8 (31%) 10 (26%)
60+ 3 (25%) 4 (15%) 7 (18%)
TOTAL 12 (101%) 26 (101%) 38 (100%)
*percentages refer to column totals.
The 38 cases of E. coli O157:H7 infection meeting the investigation case definition were reported from 10 counties. On set of illness occurred from mid-June to mid-July, peaking on June 22.
From July 16 – 19, hypothesis-generating interviews were undertaken with seven patients. These patients lived in four different counties and ranged in age from 5-69 years. Three of the patients were female.
Hypothesis-generating interviews revealed that most cases had consumed lettuce and alfalfa sprouts in the week before they became ill. No single restaurant or social event was identified in common.
APPENDIX 1. Distribution of E. coli O 157:H7 cases reported to FoodNetSites* by age group and gender, United States, 1997. (N=340)
Age group (years) Gender TOTAL
Male Female
0-<1 5 (3%) 5 (3%) 10 (3%)
1-9 77 (48%) 77 (43%) 154 (45%)
10-19 36 (22%) 18 (10%) 54 (16%)
20-29 10 (6%) 20 (11%) 30 (9%)
30-39 6 (4%) 12 (7%) 18 (5%)
40-49 7 (4%) 5 (3%) 12 (4%)
50-59 7 (4%) 17 (10%) 24 (7%)
60+ 14 (9%) 24 (13%) 38 (11%)
TOTAL 162 (100%) 178 (100%) 340 (100%)
*Foodborne Diseases Active Surveillance Network (FoodNet) is a collaborative project between CDC, the U.S. Department of Agriculture (USDA), the Food and Drug Administration (FDA), and selected state and local health departments. In 1997, FoodNet conducted population based active surveillance for confirmed cases of Campylobacter, Escherichia coli O157, Listeria,Salmonella, Shigella, Vibrio, and Yersinia infectionsin Minnesota, Oregon, and selected counties in California, Connecticut, and Georgia (total population: 16.1 million).
Module 2 – Case
MEASURING HEALTH AND DISEASE
Case Assignment
As part of a State Budget and Appropriations Subcommittee, you have been charged with reviewing health data of local health jurisdictions and establishing priorities for funding for the upcoming fiscal year.
After reviewing the following information
Eagle Rock County San Marino County Baldwin County
Population
2,490,653 299,658 250,765
>65 years 372,166 99,885 2,857
Total Population 2,862,819 399,543 253,622
Number of Deaths
4955 900 1854
>65 yrs 9,845 3,700 455
Total Deaths 14,800 4,600 2,309
Cause of Death
Coronary Heart Disease 6,200 1,800 790
Cancer 3,300 1,000 429
Homicide 3,100 800 450
Motor Vehicle Accident 2,200 1,000 640
Case Assignment
Your task is to answer these questions:
1. Calculate and compare the crude and age-specific death rates for each of the three counties (refer to the information Crude, Specific, and Adjusted Rates in the module homepage). Based on the crude death rate, which county appears to have the greatest need for funding? Does the age-specific death rate change your view regarding which county has a greater need for funding? Explain. Why is it possible to have a low crude rate and higher age-specific death rates?
2. Calculate and compare the cause-specific death rates (Use the information at http://www.pitt.edu/~super1/lecture/lec0441/001.htm from your background readings). For this, combine data from all counties. Based on the data provided, what do you think are the main health priorities?
Assignment Expectations
Length: Case assignments should be at least 2 pages (500 words) in length.
References: At least two references must be included from academic sources (e.g. peer-reviewed journal articles). Required readings are included. Quoted material should not exceed 10% of the total paper (since the focus of these assignments is critical thinking). Use your own words and build on the ideas of others. When material is copied verbatim from external sources, it MUST be enclosed in quotes. The references should be cited within the text and also listed at the end of the assignment in the References section (APA format recommended).
Organization: Subheadings should be used to organize your paper according to question
Format: APA format is recommended for this assignment. See Syllabus page for more information on APA format.
Grammar and Spelling: While no points are deducted, assignments are expected to adhere to standards guidelines of grammar, spelling, punctuation, and sentence syntax. Points may be deducted if grammar and spelling impact clarity.
The following items will be assessed in particular:
• Achievement of learning objectives for case assignment
• Relevance (e.g. all content is connected to the question)
• Precision (e.g. specific question is addressed. Statements, facts, and statistics are specific and accurate).
• Depth of discussion (e.g. present and integrate points that lead to deeper issues)
• Breadth (e.g. multiple perspectives and references, multiple issues/factors considered)
• Evidence (e.g. points are well-supported with facts, statistics and references)
• Logic (e.g. presented discussion makes sense, conclusions are logically supported by premises, statements, or factual information)
• Clarity (e.g. writing is concise, understandable, and contains sufficient detail or examples)
• Objectivity (e.g. avoid use of first person and subjective bias)
Module 2 – SLP
MEASURING HEALTH AND DISEASE
A Multistate Outbreak of E. coli 0157:H7
Click here to read the Module 2 SLP background THE MODULE 2 READING is included above

Session Long Project
Please answer these questions:
1. What are the advantages and disadvantages of the case definition?
2. Describe and compare the age and gender distribution of E. coli O157:H7 cases from this outbreak and those reported from U.S. FoodNet sites in 1997.
3. What kinds of questions would you ask in the hypothesis-generating interviews?
4. Given your knowledge about E. coli O157:H7, the descriptive epidemiology of the initial cases, and the results of hypothesis-generating interviews, outline the information available at this point on the source of the outbreak and mode of transmission
SLP Assignment Expectations
Length: SLP assignments should be at least 2 pages (500 words) in length.
References: At least two references must be included from academic sources (e.g. peer-reviewed journal articles). Required readings are included. Quoted material should not exceed 10% of the total paper (since the focus of these assignments is critical thinking). Use your own words and build on the ideas of others. When material is copied verbatim from external sources, it MUST be enclosed in quotes. The references should be cited within the text and also listed at the end of the assignment in the References section (APA format recommended).
Organization: Subheadings should be used to organize your paper according to question
Format: APA format is recommended for this assignment. See Syllabus page for more information on APA format.
Grammar and Spelling: While no points are deducted, assignments are expected to adhere to standards guidelines of grammar, spelling, punctuation, and sentence syntax. Points may be deducted if grammar and spelling impact clarity.
The following items will be assessed in particular:
• Achievement of learning objectives for SLP assignment
• Relevance (e.g. all content is connected to the question)
• Precision (e.g. specific question is addressed. Statements, facts, and statistics are specific and accurate).
• Depth of discussion (e.g. present and integrate points that lead to deeper issues)
• Breadth (e.g. multiple perspectives and references, multiple issues/factors considered)
• Evidence (e.g. points are well-supported with facts, statistics and references)
• Logic (e.g. presented discussion makes sense, conclusions are logically supported by premises, statements, or factual information)
• Clarity (e.g. writing is concise, understandable, and contains sufficient detail or examples)
• Objectivity (e.g. avoid use of first person and subjective bias)
Module 3 – Background
DESCRIPTIVE AND ANALYTIC EPIDEMIOLOGY
If you cannot locate an article in one set of databases (e.g., EBSCO), try to locate it in ProQuest.
Required Readings
A guide to research methods. Evidence based medicine and study designs at Suny Downstate Medical Center. Retrieved on May 22, 2012 from: http://library.downstate.edu/EBM2/2100.htm
Coggon, D., Rose, G., & Barker, D.J.P. (2007) Case Control and Cross-Sectional studies in Epidemiology for the Uninitiated (4th edition). British Medical Journal. Retrieved on May 22, 2012 from: http://www.bmj.com/about-bmj/resources-readers/publications/epidemiology-uninitiated
Centers for Disease Control and Prevention (2012). Lesson 1: Introduction to Epidemiology, Section 6: Descriptive Epidemiology. In Principles of Epidemiology in Public Health Practice, 3rd Edition. Retrieved March 7, 2013 at http://www.cdc.gov/osels/scientific_edu/ss1978/lesson1/Section6.html
Case Control Studies. Universigty of Pitssburg Supercourse. Retrieved on May 22, 2012 from: http://www.pitt.edu/~super1/lecture/lec8591/index.htm
Optional Readings
Schoenbach, V.J., Rosamond, V.D., Understanding the fundamentals of epidemiology. An evolving text. UNC School of Public Health. Retrieved on May 22, 2012 from: http://www.epidemiolog.net/evolving/TableOfContents.htm
Supercourse: Epidemiologic Design I: Focus on Descriptive Study. Retrieved on May 22, 2012 from: University of Pittsburgh Web site http://www.pitt.edu/~super1/lecture/lec0551/index.htm
Module 3 – Case
DESCRIPTIVE AND ANALYTIC EPIDEMIOLOGY
Case Assignment
Below is epidemiologic data collected on an unknown pathogen.
Your task for this case assignment:
1. Describe these data by person, place, and time (i.e. descriptive epidemiology). For more information on descriptive epidemiology, please refer to the Module 3 Home Page.
2. Provide possible explanations for the pattern of this disease.
Figure 1: Incidence Rate of Unknown Disease by Age and Gender

Figure 2: Geographical Distribution of Unknown Disease in the United States

Figure 3: Incidence Rate of Unknown Disease by State
Figure 4: Frequency of Unknown Disease by Month of Onset

Figure 5: Frequency of Unknown Disease by Year

Assignment Expectations
Length: Case assignments should be at least 3 pages (750 words) in length.
References: At least two references must be included from academic sources (e.g. peer-reviewed journal articles). Required readings are included. Quoted material should not exceed 10% of the total paper (since the focus of these assignments is critical thinking). Use your own words and build on the ideas of others. When material is copied verbatim from external sources, it MUST be enclosed in quotes. The references should be cited within the text and also listed at the end of the assignment in the References section (APA format recommended).
Organization: Subheadings should be used to organize your paper according to question
Format: APA format is recommended for this assignment. See Syllabus page for more information on APA format.
Grammar and Spelling: While no points are deducted, assignments are expected to adhere to standards guidelines of grammar, spelling, punctuation, and sentence syntax. Points may be deducted if grammar and spelling impact clarity.
The following items will be assessed in particular:
• Achievement of learning objectives for case assignment
• Relevance (e.g. all content is connected to the question)
• Precision (e.g. specific question is addressed. Statements, facts, and statistics are specific and accurate).
• Depth of discussion (e.g. present and integrate points that lead to deeper issues)
• Breadth (e.g. multiple perspectives and references, multiple issues/factors considered)
• Evidence (e.g. points are well-supported with facts, statistics and references)
• Logic (e.g. presented discussion makes sense, conclusions are logically supported by premises, statements, or factual information)
• Clarity (e.g. writing is concise, understandable, and contains sufficient detail or examples)
• Objectivity (e.g. avoid use of first person and subjective bias)
Module 3 – SLP
DESCRIPTIVE AND ANALYTIC EPIDEMIOLOGY
Designing an Epidemiologic Study to Test the Hypothesis
To test the hypothesis on the source of the outbreak, a case-control study was conducted from July 21-27. Thirty-one of the initial 38 persons meeting the original case definition (i.e., those not used in hypothesis generating interviews) were included as cases. It was decided that two controls would be selected for every case and would be matched to the case by age group (0-<2 years, 2-<5 years, 5-<12 years, 12-<18 years, 18-<60 years, and 60+ years) and gender.
The investigators identified controls for the study using sequential digit dialing. Exposure information among cases was collected for the 7 days before onset of illness. For controls, exposure information was collected for the 7 days before the interview and for the 7 days before the onset of illness in the matching case.
Twenty-seven case-control sets were interviewed; the remaining case-patients could not be reached.
Session Long Project
Please answer these questions:
1. How would you define controls for this study? What methods might be used to identify controls?
2. Do you agree with the investigators’ decision to match on age group and gender? Why or why not?
3. Over what time period would you examine exposures to possible risk factors for cases? For controls?
SLP Assignment Expectations
Length: SLP assignments should be at least 2 pages (500 words) in length.
References: At least two references must be included from academic sources (e.g. peer-reviewed journal articles). Required readings are included. Quoted material should not exceed 10% of the total paper (since the focus of these assignments is critical thinking). Use your own words and build on the ideas of others. When material is copied verbatim from external sources, it MUST be enclosed in quotes. The references should be cited within the text and also listed at the end of the assignment in the References section (APA format recommended).
Organization: Subheadings should be used to organize your paper according to question
Format: APA format is recommended for this assignment. See Syllabus page for more information on APA format.
Grammar and Spelling: While no points are deducted, assignments are expected to adhere to standards guidelines of grammar, spelling, punctuation, and sentence syntax. Points may be deducted if grammar and spelling impact clarity.
The following items will be assessed in particular:
• Achievement of learning objectives for SLP assignment
• Relevance (e.g. all content is connected to the question)
• Precision (e.g. specific question is addressed. Statements, facts, and statistics are specific and accurate).
• Depth of discussion (e.g. present and integrate points that lead to deeper issues)
• Breadth (e.g. multiple perspectives and references, multiple issues/factors considered)
• Evidence (e.g. points are well-supported with facts, statistics and references)
• Logic (e.g. presented discussion makes sense, conclusions are logically supported by premises, statements, or factual information)
• Clarity (e.g. writing is concise, understandable, and contains sufficient detail or examples)
• Objectivity (e.g. avoid use of first person and subjective bias)
Module 4 – Background
MEASURES OF ASSOCIATION
Required Readings
Centers for Disease Control and Prevention (CDC). (2009) Outbreak of Salmonella serotype Saintpaul infections associated with eating alfalfa sprouts – United States, 2009. MMWR Morb Mortal Wkly,;58(18):500-3. Retrieved on May 22, 2012 from: http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5818a4.htm
Meirik O., Cohort and case control studies. Retrieved May 22, 2012 from: http://www.gfmer.ch/Books/Reproductive_health/Cohort_and_case_control_studies.html
Spitalnic S (2006). Risk Assessment II: Odds Ratio. Hospital Physician, 2006 Jan: 23-26. Retrieved May 22, 2012, from http://www.turner-white.com/memberfile.php?PubCode=hp_jan06_odds.pdf
Redbook: Toxicological Principles for the Safety Assessment of Food Ingredients. U.S. Department of Health and Human Services, Food and Drug Administration, Center for Food Safety and Applied Nutrition July 2000; Updated July 2007. Retrieved May 22, 2012 from http://www.fda.gov/downloads/Food/GuidanceRegulation/UCM222779.pdf
Supercourse, Epidemiology, the Internet and Global health. Different kinds of Epidemiologic Designs. Retrieved May 22, 2012, from University of Pittsburgh Web site http://www.pitt.edu/~super1/lecture/lec0571/index.htm
Supercourse, Epidemiology, the Internet and Global health. Epidemiologic Design II, Focus on Analytic Study Retrieved May 22, 2012, from University of Pittsburgh Web site http://www.pitt.edu/~super1/lecture/lec0561/index.htm
Optional Reading
Redbook: Toxicological Principles for the Safety Assessment of Food Ingredients. U.S. Department of Health and Human Services, Food and Drug Administration, Center for Food Safety and Applied Nutrition July 2000; Updated July 2007. Retrieved May 22, 2012 from http://www.fda.gov/Food/GuidanceComplianceRegulatoryInformation/GuidanceDocuments/
FoodIngredientsandPackaging/Redbook/default
Module 4 – How to calculate an odds ratio
MEASURES OF ASSOCIATION
A2x2 table is used to calculate an odds ratio:
Disease No Disease
Exposed a b
Unexposed c d
The formula for odds ratio is:
Odds ratio = (a xd)/(b x c)
If a researcher selects 50 Lyme disease cases and 100 unmatched controls for a case-control study, and the results indicated that 45 cases and 10 controls recently hiked in a national forest, the odds ratio would be calculated as follows:
Cases Controls Total
Hiking 45 10 55
No Hiking 5 90 95
Total 50 100 150
Odds ratio = (45 x 90) ÷ (10 x 5) = 81
Module 4 – How to calculate a relative risk
MEASURES OF ASSOCIATION
A2x2 table is used to calculate a relative risk:
Disease No Disease
Exposed a b
Unexposed c d
The formula for relative risk is:
Relativerisk = (a/(a+b)) ÷ (c/(c+d))
If 5000 smokers and 5000 non-smokers were selected for a cohort study, and the results of the study indicated that 50 of the 5000 smokers developed lung cancer and 2 of the 5000 non-smokers developed cancer, relative risk would be calculated as follows:
Lung cancer No lung cancer Total
Smokers 50 4950 5000
Non-smokers 2 4998 5000
Total 52 9948 10,000
Relative risk = (50/5000) ÷(2/5000) = 25
Module 4 – Case
MEASURES OF ASSOCIATION
Case Assignment
As an epidemiologist for the County Disease Control Office, you are investigating an outbreak that occurred at a restaurant. The predominant symptoms included vomiting (81%), nausea (76%), and diarrhea (76%). The average incubation period was five hours with an average duration of 19 hours. Items consumed among the ill included prime rib, baked potato with butter, and green salad with dressing.
Figure 1:
FOOD ITEMS PERSONS WHO ATE SPECIFIED FOOD PERSONS WHO DID NOT EAT SPECIFIED FOOD
Ill Not Ill Total Ill Not Ill Total
Prime Rib 18 3 21 3 5 8
Baked Potato 19 4 23 2 4 6
Green Salad 18 9 27 1 1 2
Figure 2:
Food Item 95% Confidence Interval
Prime Rib 1.4 – 65.7
Baked Potato 1.6 -218.5
Green Salad .10 – 42.9
Case Assignment
Your task for this case assignment is to answer these questions:
1. What type of study was used for this investigation? Explain.
2. What would be the appropriate measure of association for this study?
3. Calculate the food-specific attack rates and calculate the measure of association between illness and each food item.
4. What does a confidence interval mean, and which 95% confidence intervals are statistically significant?
5. What do the results indicate regarding the likely source of exposure?
Assignment Expectations
Length: Case assignments should be at least 2 pages (500 words) in length.
References: At least two references must be included from academic sources (e.g. peer-reviewed journal articles). Required readings are included. Quoted material should not exceed 10% of the total paper (since the focus of these assignments is critical thinking). Use your own words and build on the ideas of others. When material is copied verbatim from external sources, it MUST be enclosed in quotes. The references should be cited within the text and also listed at the end of the assignment in the References section (APA format recommended).
Organization: Subheadings should be used to organize your paper according to question
Format: APA format is recommended for this assignment. See Syllabus page for more information on APA format.
Grammar and Spelling: While no points are deducted, assignments are expected to adhere to standards guidelines of grammar, spelling, punctuation, and sentence syntax. Points may be deducted if grammar and spelling impact clarity.
The following items will be assessed in particular:
• Achievement of learning objectives for case assignment
• Relevance (e.g. all content is connected to the question)
• Precision (e.g. specific question is addressed. Statements, facts, and statistics are specific and accurate).
• Depth of discussion (e.g. present and integrate points that lead to deeper issues)
• Breadth (e.g. multiple perspectives and references, multiple issues/factors considered)
• Evidence (e.g. points are well-supported with facts, statistics and references)
• Logic (e.g. presented discussion makes sense, conclusions are logically supported by premises, statements, or factual information)
• Clarity (e.g. writing is concise, understandable, and contains sufficient detail or examples)
• Objectivity (e.g. avoid use of first person and subjective bias)
Module 4 – SLP
MEASURES OF ASSOCIATION
PART IV – Analysis and Interpretation
In the case-control study, the odds ratio for alfalfa sprouts was 29, with the 95% confidence interval 7.5 – 545.2.
Session Long Project
Answer these questions
1. Is this odds ratio statistically significant? Please explain.
2. Do you think there is a causal relationship between exposure (eating alfalfa sprouts) and disease? Please explain (using the applicable criteria under “Does Association Mean Causality” in your modular homepage)
SLP Assignment Expectations
Length: SLP assignments should be at least 2 pages (500 words) in length.
References: At least two references must be included from academic sources (e.g. peer-reviewed journal articles). Required readings are included. Quoted material should not exceed 10% of the total paper (since the focus of these assignments is critical thinking). Use your own words and build on the ideas of others. When material is copied verbatim from external sources, it MUST be enclosed in quotes. The references should be cited within the text and also listed at the end of the assignment in the References section (APA format recommended).
Organization: Subheadings should be used to organize your paper according to question
Format: APA format is recommended for this assignment. See Syllabus page for more information on APA format.
Grammar and Spelling: While no points are deducted, assignments are expected to adhere to standards guidelines of grammar, spelling, punctuation, and sentence syntax. Points may be deducted if grammar and spelling impact clarity.
The following items will be assessed in particular:
• Achievement of learning objectives for SLP assignment
• Relevance (e.g. all content is connected to the question)
• Precision (e.g. specific question is addressed. Statements, facts, and statistics are specific and accurate).
• Depth of discussion (e.g. present and integrate points that lead to deeper issues)
• Breadth (e.g. multiple perspectives and references, multiple issues/factors considered)
• Evidence (e.g. points are well-supported with facts, statistics and references)
• Logic (e.g. presented discussion makes sense, conclusions are logically supported by premises, statements, or factual information)
• Clarity (e.g. writing is concise, understandable, and contains sufficient detail or examples)
• Objectivity (e.g. avoid use of first person and subjective bias)
Module 5 – Background
SCREENING FOR DISEASES
Required Readings
Loong, TZ (2003). Understanding sensitivity and specificity with the right side of the brain.
British Medical Journal (International edition), 327, 716-720. Retrieved on May 22, 2012 from ProQuest. This is the attachment.

Dechet A (2005). Foodborne Illness Outbreaks and Sprouts. FDA Public Meeting: 2005 Sprout Safety. Centers for Disease Control and Prevention. Retrieved May 22, 2012 from www.fda.gov/ohrms/dockets/dockets/05n0147/05n-0147-ts00001-dechet.ppt
Supercourse, Epidemiology, the Internet and Global health. Screening and Disease Prevention. Retrieved May 22, 2012 from University of Pittsburgh Web site Screening and Disease Prevention. (n.d.). http://www.pitt.edu/~super1/lecture/lec0721/index.htm
PATH (2008). Accuracy of Diagnostic Tests. Retrieved May 22, 2012 from http://sites.path.org/dx/rapid-dx/performance/

University of Washington (nd). Epidemiology Glossary ; Retrieved May 22, 2012 from http://depts.washington.edu/physdx/eglossary.html
Lalkhen, AG and McCluskey, A (2008). Clinical tests: sensitivity and specificity. Contin Educ Anaesth Crit Care Pain; 8(6): 221-223 doi:10.1093/bjaceaccp/mkn041. Retrieved March 7, 2013 at http://ceaccp.oxfordjournals.org/content/8/6/221.full
For the SLP
While the assignment may be based on a real case, the questions can refer to any outbreak that involved sprouts and E. coli 0157:H7. Knowing the specific pathogen (its characteristics, transmission) and the specific food, how could have the contamination occurred? You are asked to think about a possible point of contamination and about measures of control. Here is another potentially useful reference:
World Health Organization (2011). Enterohaemorrhagic Escherichia coli (EHEC). Retrieved May 22, 2012 from http://www.who.int/mediacentre/factsheets/fs125/en/
Optional Reading
Gray RH, Makumbi F, Serwadda D, et. al. (2006) Limitations of rapid HIV-1 tests during screening for trials in Uganda: diagnostic test accuracy study. BMJ, 335(7612):188. Retrieved on May 22, 2012 from http://www.bmj.com/highwire/filestream/378714/field_highwire_article_pdf/0.pdf
Module 5 – SLP Background
SCREENING FOR DISEASES
PART V – Other Investigations
Tracebacks of food are often necessary to identify sources of contamination and quickly limit a public health threat by removing these sources. One purpose of a traceback is to ascertain the distribution and production chain for a food product so that an effective recall can be undertaken. Tracebacks can also clarify the point or points at which the implicated food was likely to have become contaminated and help determine how to prevent similar outbreaks in the future. Epidemiologic tracebacks can accomplish each of these goals, but are different from the more detailed, regulatory tracebacks which follow rules of legal evidence.
An epidemiologic traceback usually begins with the information available at the time of purchase of the implicated food item and extends back to the very beginning of its production. All production steps, from harvest to consumption, are examined.
Full tracebacks leading to formal product recalls can be time-consuming and result in many dead-ends. Pertinent information and records are often missing or poorly maintained. Traceback efforts may require hundreds of hours of tedious work and may extend to other states and countries.
MDCH and CDC decided to do an epidemiologic traceback of the alfalfa sprouts implicated in the Michigan outbreak.
Of the 16 patients who ate sprouts for whom the source of the sprouts could be traced, 15 led to a single sprouting facility, facility A in Michigan; in the remaining traceback, the patient could have eaten sprouts from either facility A or facility B in Michigan. (Figure 4) Facility A and B were the only facilities that sprouted alfalfa seed in the state. Sprouts grown by facility A at the time of the outbreak came from two lots of seed: one from Idaho and one from Australia.
At this point, the investigators became aware of a concurrent outbreak of E.coli O157:H7 infection in Virginia. CDC subtyped the strains from Virginia and identified the same PFGE pattern as in the Michigan outbreak. A case-control study conducted by the Virginia Department of Health (VDH) linked the concurrent outbreak of O157:H7 infections to alfalfa sprouts.
In Virginia, the source of sprouts could be traced for 13 patients; all led to one sprouting company in Virginia. (Figure 4) The Virginia sprouting company was using a single lot of seed harvested in Idaho –the same lot as the one used at facility A in Michigan. Traceback of the seed to the distributor identified it as part of a17,000 pound lot of which 6,000 pounds still remained.
Figure 4. Traceback results of the E.coli O157:H7 investigation of alfalfa sprouts in Michigan (MI) and Virginia(VA), 1997.
The implicated seed lot was a blend of 5 lots from fields of four farmers and was harvested between 1984 and 1996. The seed processor and the farmers were located in Idaho.
Inspection of the alfalfa fields revealed three possible sources of contamination: cattle manure, irrigation water, and deer feces. Although manure is not normally applied to alfalfa fields in Idaho, cattle feed lots were common in this area and the alfalfa fields of one farmer were adjacent to a feed lot. Manure may have leaked or been illegally dumped onto the alfalfa fields or run-off water from neighboring fields, contaminated by manure, may have been used to irrigate the alfalfa fields. In addition, three of four farmers occasionally saw deer in their fields and one field was situated next to a wildlife refuge.
The seed from each of the farmers was harvested and mechanically cleaned at the same seed processing plant. The seeds were then placed in 50 lb. bags. No further processing occurred. Most of the seed was produced to plant alfalfa fields (e.g., to produce hay for livestock feed); the relatively small amount of seed used for sprouting was not handled any differently than the raw agricultural commodity seed.
Note:*A 1988 outbreak of Salmonella Saint Paul infections in Europe was linked to mung bean sprouts. A small 1990 cluster of Salmonella Anatum infections in the United States was suspected to be linked to one grower’s alfalfa sprouts, but the source of contamination was not determined. A 1994 Salmonella Bovismorbificans outbreak in Finland and Sweden was traced to Australian alfalfa seed. In 1995, it was concluded that sprouts caused an international outbreak of Salmonella Stanley, affecting persons in more than 17 states in the United States and Finland. In that same year, another multinational outbreak of salmonellosis (due to S. entericaserotype Newport) was linked to alfalfa seeds after an increase in infections was detected in Oregon and British Columbia. In 1996, almost 10,000 cases of E. coli O157:H7 occurred among school children in Japan. The outbreak was ultimately shown to be caused by radish sprouts grown from seed imported from the U.S.
Part VI Control
The implicated seed lot was not distributed to any other sprouting companies in or outside the United States. The remaining 6,000 lbs. of seed was immediately removed from the marketplace. A sample of 500 grams of seed was cultured directly, and the same amount was sprouted and then cultured; neither yielded E. coli O157:H7.
The Idaho Division of Food and Drugs held meetings at which public health officials explained to seed growers the need to protect alfalfa and other seeds used in sprouting from contamination during growing, harvesting, and packing. Both MDCH and the VDH made public television and radio announcements about the risk of contaminated sprouting seeds and recommended that persons at high risk for complications from E. coli O157:H7 infection not eat sprouts.
The Center for Food Safety and Quality Enhancement began working with the sprout industry to identify ways to make sprouts safer for human consumption. In tests with artificially inoculated seed, treating the seed by soaking it in a chlorine solution* (2000 ppm hypochlorite in 57-60EC water) at the time of sprouting reduced the level of contamination by a thousand-fold. Irradiation has also been tested and appears to work well in decontaminating sprout seeds. However, this treatment leads to diminished sprouting ability and has not been approved by the FDA.
*Chemical treatment with a hypochlorite solution is a U.S. Food and Drug Administration (FDA) approved treatment of foods.
Module 5 – Case
SCREENING FOR DISEASES
Assignment Overview
Infection with the human immunodeficiency virus (HIV) is routinely diagnosed by detecting the presence of specific antibodies in the patient’s serum. Although the presence of the virus itself can be now be detected (i.e. polymerase chain reaction [PCR] to measure plasma HIV RNA, or “viral load”), these tests remain expensive and require laboratory techniques that are not routinely available. The diagnosis of HIV infection begins with an enzyme immunoassay (EIA). The optical density (OD) of the patient’s EIA is compared to a control specimen (OD ratio). If the OD ratio is – above the established cutoff for that control sample on repeat testing the specimen is termed “repeatedly reactive”. The EIA is relatively sensitive, fast, simple and inexpensive which makes it an appropriate screening test. However, if one examines the ODs for a large group of samples from patients with and without true HIV infection you can see that there is some overlap in their EIA results if a value of A is used for the cutoff:

Hypothetical distribution of OD ratios for patients with and without HIV infection.
Hypothetical distribution of OD ratios for patients with and without HIV infection.
Patients with HIV infection are depicted with blue, thick line,those without HlV with red, thin line.
Where a cutoff is drawn to determine a diagnostic test result may be somewhat arbitrary.
Case Assignment
Answer these questions:
1. What would be the impact on this test’s sensitivity if you moved the cutoff for a positive result from A to B? What about specificity? What would happen to sensitivity and specificity if you moved the cutoff from A to C? Where would you put the cutoff for this test? What is the relationship between sensitivity and specificity for any given test?
2. Where would the director of the Blood Bank who is screening donated blood for HIV antibody want to put the cutoff? What would be the potential problem caused by this decision? Where would an investigator enrolling high-risk patients in a clinical trial for an experimental, potentially toxic antiretroviral draw the cutoff? What would be the potential problem caused by this decision? In your answer please detail possible ethical and legal issues of possible concern.
Assignment Expectations
Length: Case assignments should be at least 2 pages (500 words) in length.
References: At least two references must be included from academic sources (e.g. peer-reviewed journal articles). Required readings are included. Quoted material should not exceed 10% of the total paper (since the focus of these assignments is critical thinking). Use your own words and build on the ideas of others. When material is copied verbatim from external sources, it MUST be enclosed in quotes. The references should be cited within the text and also listed at the end of the assignment in the References section (APA format recommended).
Organization: Subheadings should be used to organize your paper according to question
Format: APA format is recommended for this assignment. See Syllabus page for more information on APA format.
Grammar and Spelling: While no points are deducted, assignments are expected to adhere to standards guidelines of grammar, spelling, punctuation, and sentence syntax. Points may be deducted if grammar and spelling impact clarity.
The following items will be assessed in particular:
• Achievement of learning objectives for case assignment
• Relevance (e.g. all content is connected to the question)
• Precision (e.g. specific question is addressed. Statements, facts, and statistics are specific and accurate).
• Depth of discussion (e.g. present and integrate points that lead to deeper issues)
• Breadth (e.g. multiple perspectives and references, multiple issues/factors considered)
• Evidence (e.g. points are well-supported with facts, statistics and references)
• Logic (e.g. presented discussion makes sense, conclusions are logically supported by premises, statements, or factual information)
• Clarity (e.g. writing is concise, understandable, and contains sufficient detail or examples)
• Objectivity (e.g. avoid use of first person and subjective bias)

Module 5 – SLP
SCREENING FOR DISEASES
Please answer the questions
1. Knowing the pathogen and its characteristics (including modes of transmission) where do you think was the most likely point of contamination in the production of the sprouts? In inspecting the alfalfa fields and harvesting process, what possible points of contamination should be considered?
2. What interventions/control measures would you suggest? Why?
3. In preparing a report of this investigation what possible strengths and limitations should be discussed?”
SLP Assignment Expectations
Length: SLP assignments should be at least 2 pages (500 words) in length.
References: At least two references must be included from academic sources (e.g. peer-reviewed journal articles). Required readings are included. Quoted material should not exceed 10% of the total paper (since the focus of these assignments is critical thinking). Use your own words and build on the ideas of others. When material is copied verbatim from external sources, it MUST be enclosed in quotes. The references should be cited within the text and also listed at the end of the assignment in the References section (APA format recommended).
Organization: Subheadings should be used to organize your paper according to question
Format: APA format is recommended for this assignment. See Syllabus page for more information on APA format.
Grammar and Spelling: While no points are deducted, assignments are expected to adhere to standards guidelines of grammar, spelling, punctuation, and sentence syntax. Points may be deducted if grammar and spelling impact clarity.
The following items will be assessed in particular:
• Achievement of learning objectives for SLP assignment
• Relevance (e.g. all content is connected to the question)
• Precision (e.g. specific question is addressed. Statements, facts, and statistics are specific and accurate).
• Depth of discussion (e.g. present and integrate points that lead to deeper issues)
• Breadth (e.g. multiple perspectives and references, multiple issues/factors considered)
• Evidence (e.g. points are well-supported with facts, statistics and references)
• Logic (e.g. presented discussion makes sense, conclusions are logically supported by premises, statements, or factual information)
• Clarity (e.g. writing is concise, understandable, and contains sufficient detail or examples)
• Objectivity (e.g. avoid use of first person and subjective bias)
Answer questions separately in a paragraph each with a cited source for each
1 Explain the importance of epidemiology for informing scientific, ethical, economic and political discussion of health issues.

2 Please choose an infectious disease (e.g. TB) and list which disease you have chosen. Then, please identify key sources of data that can be used to detect and control this disease in non-endemic countries. In your view are these sources of data sufficient?

3 Descriptive epidemiology involves examining the patterns of disease by person, place, and time. Descriptive epidemiology may also be used to distinguish a natural outbreak from an intentional outbreak (i.e. bioterrorism). In the American Anthrax Outbreak of 2001 (http://www.ph.ucla.edu/epi/bioter/detect/antdetect_intro.html), what were the initial epidemiologic clues that indicated that the outbreak may have been intentional?

4 Foodborne disease is a significant problem as discussed in this article: http://wwwnc.cdc.gov/eid/article/3/4/97-0414_article.htm According to this article, what are some of the factors contributing to this problem and what strategies would you propose to address this problem?

5 One of the problems in medicine and epidemiology today is the emergence of superbugs or multi-resistant bacteria. What are some of the factors that have contributed to antibiotic resistance? What strategies would you propose to address this problem?
CDC (2011) Antimicrobial Resistance Posing Growing Health Threat. Retrieved from http://www.cdc.gov/media/releases/2011/p0407_antimicrobialresistance.html
Optional reading:
CDC (2010) Antibiotic Resistance and the Threat to Public Health, Statement of Thomas Frieden, M.D., M.P.H. before Committee on Energy and Commerce Subcommittee on Health United States House of Representatives. Retrieved from ttp://www.cdc.gov/drugresistance/pdf/FriedenTestimony42810.pdf