epidemology homework (Due tomorrow before 4 pm)

Fall, 2018

Final Examination

Part B

Name: Date: 12/5/2018

Please perform calculations and respond to the following questions.

1. One hundred and eight (108) cases of staphylococcal food poisoning were reported in a rural community in August 1989. Incubation period was 2-6 hours. First case occurred at 8:00 p.m., August 6 and last case occurred at 4:00 a.m., August 7, 1989. Peak of cases was at 10:00 p.m.

Based on the information provided above, what was the most likely period of exposure to the source of epidemic among the cases? (5 points)

1. An outbreak of 110 cases of gastroenteritis occurred at a liberal arts college with a student enrollment of 1164. Having identified the meal to which the students most probably were exposed, and knowing each student’s time of onset of symptoms, it was possible to calculate incubation periods for 101 students.

From a summary line listing of incubation periods (in one-hour intervals) and number of cases, calculate the median incubation period of cases in hours.

(6 points)

Incubation Period (in hours) Number of Cases

1. (fi)

_______________________ ______________

8 22

9 11

10 18

11 8

1. 42

______________________________________________________

Total 101

1. The Second Avenue School of the Tiller County School District has an enrollment of 271 pupils. During October and November, 71 of these pupils were absent with measles.

2. What was the attack rate for measles in the Second Avenue School during October and November? (4 points)

2. The 71 pupils with measles had 93 brothers and sisters at home. Of the 93,

21 developed measles. What was the secondary attack rate in the brothers

and sisters? (4 points)

1. During the evening of July 4, a total of 17 persons were given emergency

treatment at a suburban community hospital for a condition diagnosed as staphylococcal intoxication. Interviews with these persons led to the identification of an additional 39 people who were ill with signs and symptoms compatible with staphylococcal intoxication but who did not seek medical attention. Further investigation revealed that all the ill persons and 42 others who did not become ill had attended an all-day picnic on July 4.

What is the attack rate of staphylococcal intoxication among the group that attended the picnic? (5 points)

1. Using the information in situation #4 above, 14 of the cases and 37 of the well

persons were females

(a). Calculate the sex-specific attack rates. (10 points)

(b). Calculate the ratio of the rate in males to the rate of females. Interpret the

ratio. (5 points)

6. Again, using the information in situation #4 above, upon further investigation, 53

of the ill persons and 3 of the well persons could definitely remember they had

eaten potato salad that had been prepared at the home of one of the families

attending the picnic. All other persons at the picnic denied having eaten any

potato salad.

Calculate the attack rate among those persons who claimed not to have eaten any

of the potato salad. (5 points)

7. According to a census data (1970), 4,648,377 persons lived in a rural town in West Malaysia. During the same year, census data showed that 3,409,169 persons were residing in Washington State, U.S.A., a predominantly industrialized society. Mortality data indicated the age-specific death rates for Malays in West Malaysia exceeded those for residents of Washington State for every age group by substantial margin. Yet the overall crude death rate for Washingtonians exceeded that for Malays (8.8 per 1,000 vs. 7.6 per 1,000).

From the data in the table below, perform calculations and answer the following questions:

1. Calculate the age-adjusted death rate for Malays, using the population of Washington State as the standard population. (8 points)

(b) In contrast to the crude death rate for Malays, how does the adjusted Malay rate

compare with the crude rate for Washington State? (8 points)

Age Standardization Computation

Age Groups Mortality Rates Washington State Expected

(Years) (Malays) Population Deaths

_______________________________________________________________________

0-4 15.0 280,472

5-14 1.6 677,339

15-24 1.6 625,867

25-34 2.7 432,102

35-44 4.3 373,848

45-54 9.9 392,654

55-64 24.9 304,906

65+ 70.1 322,061