1. An outbreak of food poisoning occurred among the 400 staff and patients at th
ID: 3042480 • Letter: 1
Question
1.An outbreak of food poisoning occurred among the 400 staff and patients at the Maplewood nursing home a few hours after eating dinner. Among the 60 people who became ill, the symptoms were mainly nausea, vomiting, and diarrhea. The infection-control nurse investigated the outbreak and reported results in the table below. (1 point)
Table 1. Foodborne outbreak at the Maplewood nursing home
Food item
DID EAT the specific food
DID NOT EAT the specific food
Number of people
Number of ills
Attack rates (per 100)
Number of people
Number of ills
Attack rates
(per 100)
Apple juice
100
15
300
45
Cantaloupe
80
11
320
49
Hot dog
130
25
270
35
Taco salad
150
20
250
40
Egg salad
140
50
260
10
Apple pie
170
25
230
35
What is the overall attack rate? (0.25 point)
What are the food-specific attack rates for those who ate and did not eat the food, each food item? (0.5 point)
Which food item is the most likely cause of this outbreak? (0.25 point)
Table 1. Foodborne outbreak at the Maplewood nursing home
Food item
DID EAT the specific food
DID NOT EAT the specific food
Number of people
Number of ills
Attack rates (per 100)
Number of people
Number of ills
Attack rates
(per 100)
Apple juice
100
15
300
45
Cantaloupe
80
11
320
49
Hot dog
130
25
270
35
Taco salad
150
20
250
40
Egg salad
140
50
260
10
Apple pie
170
25
230
35
Explanation / Answer
Overall attack rate is the total number of new cases divided by the total population
Overall Attack Rate = (146 + 214)/ (770 + 1630) = 0.15
(b) Food specific rates are given above for each item.
(c) The food item which has the maximum difference in atack rate, which is, the Egg salad cause the outbreak.
Table 1. Foodborne outbreak at the Maplewood nursing home Food item DID EAT the specific food DID NOT EAT the specific food Number of people Number of ills Attack rates (per 100) Number of people Number of ills Attack rates (per 100) Apple juice 100 15 15 300 45 15 Cantaloupe 80 11 13.75 320 49 15.3125 Hot dog 130 25 19.2308 270 35 12.9630 Taco salad 150 20 13.3333 250 40 16 Egg salad 140 50 35.7143 260 10 3.8462 Apple pie 170 25 14.7059 230 35 15.2174 Sum 770 146 18.9610 1630 214 13.1288Related Questions
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