1. Which of the following is a condition which may occur during the incubation period?

• Which of the following is a condition which may occur during the incubation period?
• Transmission of infection
• Chicken pox is a highly communicable disease. It may be transmitted by direct contact

with a person infected with the varicella-zoster virus (VZV). The typical incubation time is between 10 to 20 days. A boy started school 2 weeks after showing symptoms of chicken pox including mild fever, skin rash, and fluid-filled blisters. One month after the boy returned to school, none of his classmates had been infected by VZV. The main reason

was:

• Contact was after infectious period
• The ability of a single person to remain free of clinical illness following exposure to an

infectious agent is known as:

• Immunity
• Which of the following is characteristic of a single-exposure, common-vehicle outbreak?
• The epidemic curve has a normal distribution when plotted against the logarithm

of time

• What is the diarrhea attack rate in persons who ate both ice cream and pizza?
• 39/52
• What is the overall attack rate in persons who did not eat ice cream?
• 33%
• Which of the food items (or combination of items) is most likely to be the infective

item(s)?

• Ice cream only
• Which of the following reasons can explain why a person who did not consume the

infective food item got sick?

• All of the above
• An outbreak of gastroenteritis occurred at a boarding school with a student enrollment of
• Fifty-seven students reported symptoms including vomiting, diarrhea, nausea, and

low-grade fever between 10 p.m. on September 24 and 8 p.m. on September 25. The ill students lived in dormitories that housed 723 of the students. The table below provides information on the number of students per type of residence and the number reporting illnesses consistent with the described symptoms and onset time. Calculate the attack rate among all students at the boarding school.

• 6.7%
• An outbreak of gastroenteritis occurred at a boarding school with a student enrollment of
• Fifty-seven students reported symptoms including vomiting, diarrhea, nausea, and

low-grade fever between 10 p.m. on September 24 and 8 p.m. on September 25. The ill students lived in dormitories that housed 723 of the students. The table below provides information on the number of students per type of residence and the number reporting illnesses consistent with the described symptoms and onset time. Calculate the attack rates for boys and girls separately

• Boys: 10.1% girls : 3.3%
• An outbreak of gastroenteritis occurred at a boarding school with a student enrollment of
• Fifty-seven students reported symptoms including vomiting, diarrhea, nausea, and

low-grade fever between 10 p.m. on September 24 and 8 p.m. on September 25. The ill students lived in dormitories that housed 723 of the students. The table below provides information on the number of students per type of residence and the number reporting illnesses consistent with the described symptoms and onset time. What is the proportion of total cases occurring in boys?

• 75.%
• An outbreak of gastroenteritis occurred at a boarding school with a student enrollment of
• Fifty-seven students reported symptoms including vomiting, diarrhea, nausea, and

low-grade fever between 10 p.m. on September 24 and 8 p.m. on September 25. The ill students lived in dormitories that housed 723 of the students. The table below provides information on the number of students per type of residence and the number reporting illnesses consistent with the described symptoms and onset time. What is the proportion of total cases occurring in students who live in dormitories? 1 / 3

• 91.2%
• An outbreak of gastroenteritis occurred at a boarding school with a student enrollment of
• Fifty-seven students reported symptoms including vomiting, diarrhea, nausea, and

low-grade fever between 10 p.m. on September 24 and 8 p.m. on September 25. The ill students lived in dormitories that housed 723 of the students. The table below provides information on the number of students per type of residence and the number reporting illnesses consistent with the described symptoms and onset time. Which proportion is more informative for the purpose of the outbreak investigation?

• Both proportions are useful. Dormitory residents account for over 90% of the

cases indicating an outbreak of an infectious agent that was transmitted at the school. Furthermore, over 75% of the cases were boys indicating that the responsible agent was more likely to have been transmitted in the boys’ dormitory.

• A group of researchers are interested in conducting a clinical trial to determine whether a

new cholesterol-lowering agent was useful in preventing coronary heart disease (CHD).They identified 12,327 potential participants for the trial. At the initial clinical exam, 309 were discovered to have CHD. The remaining subjects entered the trial and were divided equally into the treatment and placebo groups. Of those in the treatment group, 505 developed CHD after 5 years of follow-up while 477 developed CHD during the same period in the placebo group. What was the prevalence of CHD at the initial exam?

• 25.1
• A group of researchers are interested in conducting a clinical trial to determine whether a

new cholesterol-lowering agent was useful in preventing coronary heart disease (CHD).They identified 12,327 potential participants for the trial. At the initial clinical exam, 309 were discovered to have CHD. The remaining subjects entered the trial and were divided equally into the treatment and placebo groups. Of those in the treatment group, 505 developed CHD after 5 years of follow-up while 477 developed CHD during the same period in the placebo group. What was the incidence of CHD during the 5-year study?

• 81.7
• Which of the following are examples of a population prevalence rate?
• The number of persons with hypentension per 100,000 population
• What would be the effect on age-specific incidence rates of uterine cancer if women with

hysterectomies were excluded from the denominator of incidence calculations assuming that most women who have had hysterectomies are older than 50 years of age

• Rates would increase in women older than 50 years of age but may decrease in

younger women as they get older

• A survey was conducted among 1,000 randomly sampled adult males in the United

States in 2005. The results from this survey are shown below.

The researchers stated that there was a doubling of risk of hypertension in each age group younger than 60 years of age. You conclude that the researchers’ interpretation:

• Is incorrect because prevalence rates are estimated
• The incidence and prevalence rates of a chronic childhood illness for a specific

community are given below.

Based on the data, which of the following interpretations best describes disease X?

• The duration of disease is becoming shorter
• A prevalence survey conducted from January 1 through December 31, 2003 identified

580 new cases of tuberculosis in a city of 2 million persons. The incidence rate of tuberculosis in this population has historically been 1 per 4,000 persons each year. What is the incident rate of tuberculosis per 100,000 persons in 2003?

• 29
• A prevalence survey conducted from January 1 through December 31, 2003 identified

580 new cases of tuberculosis in a city of 2 million persons. The incidence rate of tuberculosis in this population has historically been 1 per 4,000 persons each year. Has the risk of tuberculosis increased or decreased during 2003? 2 / 3

• Increased
• Which of the following is an advantage of active surveillance?
• More accurate due to reduced reporting burden for health care providers
• The population of a city on February 15, 2005, was 36,600. The city has a passive

surveillance system that collects hospital and private physician reports of influenza cases every month. During the period between January 1 and April 1, 2005, 2,200 new cases of influenza occurred in the city. Of these cases, 775 persons were ill with influenza according to surveillance reports on April 1, 2005. The monthly incidence rate of active

cases of influenza for the 3-month period was:

• 20 per 1000 populaiton
• The population of a city on February 15, 2005, was 36,600. The city has a passive

surveillance system that collects hospital and private physician reports of influenza cases every month. During the period between January 1 and April 1, 2005, 2,200 new cases of influenza occurred in the city. Of these cases, 775 persons were ill with influenza according to surveillance reports on April 1, 2005. The prevalence rate of active influenza

as of April 1, 2005, was:

• 20 per 1000 population
• The population of a city on February 15, 2005, was 36,600. The city has a passive

surveillance system that collects hospital and private physician reports of influenza cases every month. During the period between January 1 and April 1, 2005, 2,200 new cases of influenza occurred in the city. Of these cases, 775 persons were ill with influenza according to surveillance reports on April 1, 2005. What can be inferred about influenza cases occurring in the city?

• The average duration of influenza is approximately 1 month
• A study found that adults older than age 50 had a higher prevalence of pneumonia than

those who were younger than age 50. Which of the following is consistent with this finding?

• Incidence rates do not vary by age, but older adults have pneumonia for a longer

duration compared to younger adults

• Which of the following statements are true? More than one answer may be correct.
• Prevalence rates are useful for public health planning
• Incidence rates can be used to estimate prevalence when the mean duration of

the disease is known

• A disease has an incidence of 10 per 1,000 persons per year, and 80% of those affected

will die within 1 year. Prior to the year 2000, only 50% of cases of the disease were detected by physician diagnosis prior to death. In the year 2000, a lab test was developed that identified 90% of cases an average of 6 months prior to symptom onset; however, the prognosis did not improve after diagnosis. Comparing the epidemiology of the disease prior to 2000 with the epidemiology of the disease after the development of the lab test, which statement is true concerning the disease in 2000?

• Incidence is higher and prevalence is higher than in 1999
• A disease has an incidence of 10 per 1,000 persons per year, and 80% of those affected

will die within 1 year. Prior to the year 2000, only 50% of cases of the disease were detected by physician diagnosis prior to death. In the year 2000, a lab test was developed that identified 90% of cases an average of 6 months prior to symptom onset; however, the prognosis did not improve after diagnosis. Which statement is true concerning the duration of the disease after the development of the lab test?

• Mean duration of case of the disease is longer in 2000
• A disease has an incidence of 10 per 1,000 persons per year, and 80% of those affected

will die within 1 year. Prior to the year 2000, only 50% of cases of the disease were detected by physician diagnosis prior to death. In the year 2000, a lab test was developed that identified 90% of cases an average of 6 months prior to symptom onset; however, the prognosis did not improve after diagnosis. Which statement is true concerning the disease-specific mortality rate after the development of the lab test?

• The mortality rate for the disease is the same 2000
• / 3