Question

On a cruise ship there are 1,000 people. There is a GI infection outbreak traced to a particular dinner served at one of the restaurants on the cruise ship. 395 people dined at the restaurant in question for that dinner, and of those 275 had the particular dinner that was the source of the outbreak. In total, there were 215 primary cases who suffered from the GI infection. 1) What was the attack rate? Express your answer as rate per 100 people. The causative agent in the particular dinner was narrowed down to either steak or shrimp. 55 people ate only the shrimp, and of these 48 became sick. 90 people ate only the steak, and of these 54 became sick. 130 people ate both the steak and shrimp and 113 people became sick. 2) What is the most likely individual food that caused the infection?

Answer 1

Answer :

Q)

Total population = 1000

Exposure or people at risk = 275

Primary cases = 215

Attack rate per 100 population =

(primary case/people at risk) X 100

= (215/275)X100 = 78.18%

Attack rate = 78.18%

Q)

Exposure to shrimp = 55

Primary case from shrimp = 48

Attack rate from shrimp = (48/55) X 100

= 87.27%

Exposure to steak = 90

Primary case from steak = 54

Attack rate from steak = (54/90)X100

=60%

Combined exposure = 130

Primary case from combined exposure = 113

Attack rate of combined exposure = (113/130)X100

= 86.92%

So most likely individual food caused infection is from SHRIMP.