investigation of foodborne outbreak on a cruise ship

CASE STUDY 2 INSTRUCTIONS

You will assume the role of the investigator for the following foodborne illness case file.  You will analyze the data, determine attack rates, and perform the statistical calculations necessary to find and association with disease and determine a likely source of the outbreak.  (Hint: graphs and tables included in this case file may be useful). You will then develop a plan to stop the propagation of the outbreak and create an educational program for food handlers to highlight prevention of a similar outbreak in the future. You should ensure that all practices and recommendations are in accordance with the regulations of the governing agency.  You should include a reference page with a minimum of 5 sources from government publications.  The paper should be 8 pages, double-spaced, and include formatting consistent with either the APA or AMA style guide. Case Study 2 is due by 11:59 p.m. (ET) on Sunday of Module/Week 7.

Case: You have just finished your MPH at Liberty University and have taken a position with the CDC in the Vessel Sanitation Program (VSP). Today, you have been asked to participate in an investigation of the outbreak of a diarrheal illness aboard the cruise ship Warped Imagination bound to Miami from a Caribbean voyage.

In accordance with VSP protocol, the chief medical officer on board the ship has kept a log of illness among the crew and passengers. Sick passengers and crew were instructed to begin a BRAT diet (bananas, rice, apple sauce, tea, and toast).  Normally a formal count would be presented to the VSP 36 hours prior to arrival in the US; however, on the fifth day of the trip a total of 67 cases of diarrheal illness had been recorded among the 2500 passengers and 3 cases of a similar illness among the 1200 crew.  Afflicted crew members and all food handlers have been removed from duty.  It is now the 6th day of the trip and, since the case load has reached the 2% threshold for passengers, the medical staff has filed the mandatory report of the situation to the VSP.

The ship has made ports of call at Key West; Ocho Rios, Jamaica; Cozumel, Mexico; Belize; and Grand Cayman.  The remaining ports of call have been canceled and the ship is en route to Miami as the capacity of the medical staff to provide care may soon be exceeded by the case load of victims requiring IV therapy. The captain expects to make it to Miami within about 48 hours provided the weather cooperates.

The first case of the illness was logged on the second day of the cruise about 4 hours after departing from Ocho Rios. The index case is a 26 year-old newlywed white female from Philadelphia.  Her husband has not experienced any symptoms. The wedding was the day prior to their departure from Philadelphia. Their only meal the day of the wedding was a catered dinner of chicken and beef barbeque, mashed potatoes, mixed steamed vegetables, a tossed salad, wedding cake, fruit punch and a glass of champagne. The caterer also provided a box of leftovers which the couple snacked on that evening and again just prior to leaving for the airport on the day the cruise began. They consumed only the complimentary Coke and pretzel snacks during their flight between the time they left home and the time when they had boarded the ship went to the buffet as soon as they could. The couple disembarked at Key West, the first port of call, where they ate Key Lime Pie and coffee.  The couple had no water, alcoholic beverages or other food while ashore.  That evening they were among the first passengers to eat from the buffet on the ship (See Table 1 for her food diary). The woman was feeling a bit of malaise and wanted to retire early. The following day, the couple had a light breakfast of fruit, yogurt, toast and coffee aboard ship just before making the port of call in Jamaica. The woman claims to have had no appetite that morning and while ashore only sipped a bottle of water acquired from the ship.  She consumed no food in Ocho Rios. Her husband had a cola and salt fish.
TABLE 1    onboard food consumption by index case
foods eaten    day 1    day 2    day 3    day 4    day 5
coffee    yes    yes    no    no    no
hot tea    no    no    yes    yes    yes
iced tea    no    no    yes    yes    yes
fountain drink    no    no    yes    yes    yes
ice    yes    yes    yes    yes    yes
watermelon    yes    yes    no    no    no
pineapple    yes    yes    no    no    no
cantaloupe    yes    yes    no    no    no
grapefruit    yes    yes    no    no    no
passion fruit    yes    yes    no    no    no
kiwi    yes    yes    no    no    no
papaya    yes    yes    no    no    no
banana    no    yes    yes    yes    yes
apple juice    yes    yes    no    no    no
prime rib    yes    no    no    no    no
Hawaiian ham    yes    no    no    no    no
green beans    yes    no    no    no    no
carrots    yes    no    no    no    no
creamed corn    yes    yes    no    no    no
broccoli    yes    no    no    no    no
tossed salad    yes    no    no    no    no
white rice    no    yes    yes    yes    yes
boiled potato    yes    no    no    no    no
cole slaw    yes    no    no    no    no
tomato slices    yes    yes    no    no    no
yogurt    no    yes    no    no    no
white bread    yes    no    no    no    no
apple sauce    no    yes    yes    yes    no
ice cream    yes    no    no    no    no
apple pie    yes    no    no    no    no
cheese cake    yes    no    no    no    no

Ten additional cases were diagnosed by the medical staff the fourth day of the voyage and a total of 70 cases was either diagnosed or self-reported by the fifth day (Table 2).  The predominant symptoms reported are vomiting and diarrhea.  A low grade fever is variable.  Everyone afflicted, including the index case, continued to have intermittent diarrhea and loss of appetite when the initial report was made to VSP.
Table 2    onset of cases aboard cruise ship
day 1    day 2    day 3    day 4    day 5
new passenger cases    0    1    0    7    59
new crew cases    0    0    0    3    0
total new cases    0    1    0    10    59
total cumulative cases    0    1    1    11    70
non ill    3700    3699    3699    3689    3630

Detailed food diaries during port of calls for each victim are not available; however, only passengers and crew who have consumed food from the ship’s buffet have become ill. Table 3 is a working spreadsheet of foods consumed by the passengers and crew from the buffet while on board the ship comparing afflicted and non-afflicted individuals.

TABLE 3: Food Consumption from Buffet Aboard Warped Imagination
afflicted passengers and crew     non-afflicted passengers and crew
foods eaten    day 1    day 2    day 3    day 4    day 5    day 1    day 2    day 3    day 4    day 5
bacon    43***    37***    34***    10    0    3000    2763    2879    2556    2865
sausage    24    12    0    12    0    1287    1534    1302    698    779
fried ham    12    17    12    7    0    615    863    827    793    654
pancakes    28    63    27    24    0    1377    3312    1743    1752    1297
French toast    34    12    26    18    0    2300    1389    1476    1576    1681
scrambled eggs    47***    43***    39***    37    0    2548    2334    2089    2192    2212
cold cereal    15    15    12    10    0    800    778    731    803    768
skim milk    66    66    66    57    0    3478    3478    3478    3478    3478
whole milk    3    3    3    0    0    175    175    175    175    175
coffee    70***    70***    69***    59**    0    3497    3512    3612    3597    3581
hot tea    40    40    41    47***    70***    2069    2109    2211    2075    2075
iced tea    40    40    41    47    70***    2081    1056    2112    2333    2100
fountain drink    49***    53***    54***    63***    61***    2217    2749    2757    2566    2239
ice    70***    70***    70***    70***    70***    3630    3618    3624    3630    3630
oatmeal    1    2    1    1    0    122    103    99    76    61
watermelon    60***    60***    60***    50    0    968    763    428    534    677
pineapple    45*    45    40    30    0    2413    2425    2451    2312    2433
cantaloupe    47***    47***    45***    35    0    1287    1286    1290    1301    1287
grapefruit    12    15*    15    11    0    778    779    783    775    715
passion fruit    30    35    45    43    0    1563    1823    2345    2330    2312
kiwi    30    35    35    35    0    1547    1837    1832    1815    1821
papaya    46    47    44    39    0    2401    2412    2397    2076    2073
banana    50***    53***    59***    49***    70***    2593    2852    3112    3018    2987
apple juice    55    54    49    47*    65**    2853    2853    2597    2540    2543
grapefruit juice    0    0    0    0    0    1238    1227    1199    1328    1213
hamburger    70***    70***    70***    59    0    2567    2312    2214    2237    2412
fried chicken    23    14    12    30    0    1296    769    756    1612    987
prime rib    70***    69    58    43    0    3630    3627    3200    2300    2413
Hawaiian ham    59    53    36    38    0    3085    2714    1869    2078    2217
green beans    68**    60    60    53    0    3530    3121    3108    3123    3119
carrots    63    60    38    41    0    3269    3114    1999    2133    2210
creamed corn    35    38***    34    31    0    1036    667    623    519    543
broccoli    33    45    27    28    0    1813    2334    1554    1563    1567
tossed salad    41    63    40    32    0    2232    3278    3206    2111    2328
white rice    53***    48***    43***    70***    70***    2750    2599    2319    2526    2417
mashed potatoes    69***    67*    65    54    0    3602    3526    3418    3515    3591
boiled potatoes    52*    50    54    36    0    2704    2594    2852    2598    2419
potato salad    43    37*    40    13    0    2333    2071    2075    2140    2167
cole slaw    34    33    33    12    0    1728    1823    1873    1856    1917
tomato slices    70***    70***    69**    59    0    3387    1292    1721    1312    1097
asparagus    33    12    25    0    0    1847    1783    1299    1717    787
yogurt    40    12    18    0    0    2047    1555    1113    1719    1982
leaf lettuce    15    33    39    26    0    863    1888    2077    1350    1613
cheddar cheese    25    25    27    23    0    3312    1543    1397    1192    2109
white bread    35    35    35    35    70***    1763    1918    2019    1815    1772
apple sauce    13    17    14    11***    70***    694    893    771    663    894
ice cream    20    23    24    21    0    1067    1284    1281    1093    1123
apple pie    56*    53*    49*    48    0    2988    2748    2587    2554    2548
chocolate cake    66**    67*    56*    43    0    3423    3478    3005    3397    3414
cheese cake    61    60*    58*    48    0    3400    3200    3010    3111    3093
* indicates food consumed by a sickened crewmember

CASE STUDY 2 GRADING RUBRIC

Criterion
Points Possible    Points Earned    Comments from Instructor
Comprehensive analysis of the data    20
Statistical calculations demonstrate an association with disease and determine a likely source of outbreak     30
Identification of probable source(s)    20
Actions taken to stop outbreak    40
Educational program for food handlers that highlights prevention of similar outbreak from reoccurring    40
Minimum of 5 appropriate references at 6 pts. each    30
Formatting of the paper and reference page should be consistent with either the APA or AMA style guide    20
Total Points    200