A local health department epidemiologist investigated an
outbreak of gastrointestinal illness thought to be associated with
a college cafeteria. There were many complaints about the quality
of the cafeteria’s offerings, and it appeared that the student’s
worst expectations were confirmed when several students visited the
college’s infirmary during the middle of the night and the
following day complaining of nausea, diarrhea, fever, vomiting, and
cramps. The health department’s investigation revealed that 24
students had eaten in the cafeteria and the development of active
symptoms ranged from 24 to 36 hours. A list of foods eaten, the
number of persons eating the foods, and the tabulations of illness
are presented.

a. First fill in the attack rates for those who
ate the foods and who didn’t each the foods where indicated in
table 1 located on page two.

Next, on the basis of your calculations answer questions
on page two and three.

Table 1. Data from a Foodborne Illness Outbreak in a
College Cafeteria

Note. The tuna salad was prepared from fresh
ingredients approximately 1 hour before consumption and stored
under refrigeration.

What food or foods would you suspect caused the problem?
(Review table on page 2.)

Based on the description of the clinical symptoms what
agent(s) do you think was (were) responsible? ( Your best guess, no
points will be deducted for wrong answers to this
question)

Calculate the rate differences. The Rate Difference is
the rate of disease in the exposed or ill population minus the rate
of disease in the unexposed or well population. Using the data in
2A calculate the rate difference for each food.