Question

An outbreak of E.coli occurred after a Healthy Department luncheon, which was attended by 488 faculty and staff. Assume everyone ate the same food item. 46 people had fever and diarrhea, five of these people were severely affected. Subsequent laboratory tests on everyone who attended the luncheon revealed an additional 65 cases. Calculate the attack rate of E.coli. In your own words, interpret the results.

Answer 1

Calculation-

Total people who attended luncheon are he total people at risk of infection =488.....(A)

People with fever - 46 (5 severely ill)....…(i.)

People confirmed with E.coli infection after lab tests - 65......(ii.)

Total people affected by E.coli = i. + ii. =46 + 65 =111...(B)

The attack rate of a particular disease is calculated as the number of people who became ill for a particular organism divided by the number of people at risk for the illness , and in this case for Ecoli-

(A)÷(B)

111 ÷ 488 = 0.2274

In percentage, 0.2274 × 100 = 22.74 %

So in this case of E.coli outbreak the attack rate is 22.74 %.