NR 503 Week 8 Final Exam; Student Consult
Questions with Rationale
(Complete solutions and resources for the exam)
Question 1
Which of the following is a condition which may occur during the incubation period?
• Onset of clinical illness
• Receipt of infection
• Signs and symptoms of disease
Transmission of infection
• Isolation of disease carrier through quarantine
Rationale: The incubation period is defined as the interval from receipt of infection to the time
of onset of clinical illness. Accordingly, individuals may transmit infectious agents during the
incubation period as they show no signs of disease that would enable the isolation of sick
individuals by quarantine.
Question 2
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:
• Herd immunity
• All had been immunized prior to the school year
Contact was after infectious period
• Subclinical infections were not yet detected
• Disease was endemic in the class
,The disease is spread by contact with an infected individual who can transmit the agent (VZV)
to immunologically naive persons during the incubation period and for several days after onset
of clinical illness. Since the boy started school 14 days after showing signs consistent with
chicken pox, it is most likely that he was no longer infectious.
Question 3
The ability of a single person to remain free of clinical illness following exposure to an infectious
agent is known as:
• Hygiene
• Vaccination
• Herd immunity
Immunity
• Latency
Immunity is the capacity of a single individual to avoid disease susceptibility when exposed to
an infectious agent. Herd immunity is a population characteristic. For certain diseases,
individual immunity can be acquired by vaccination, but this is not true for all infectious
Question 4
Which of the following is characteristic of a single-exposure, common-vehicle outbreak?
• Long latency period before many illnesses develop
• There is an exponential increase in secondary cases following initial exposures
• Cases include only those who have been exposed to sick persons
The epidemic curve has a normal distribution when plotted against the logarithm of time
• Wide range in incubation times for sick individuals
Single-exposure, common-vehicle outbreaks involve a sudden, rapid increase in cases of disease
that are limited to persons who share a common exposure. Additionally, few secondary cases
develop among persons exposed to primary cases. A histogram of the outbreak can plot the
number of cases by time of disease onset. In single-exposure, common-vehicle outbreaks, a log
transformation of the time of disease onset will often take on the characteristic shape of a
normal distribution (i.e., a bell curve) with the median incubation time found at the peak of the
curve.
What is the diarrhea attack rate in persons who ate both ice cream and pizza?
, 39/52
• 21/70
• 39/67
• 51/67
• none of the above
The attack rate in this example is defined as the number of persons who develop diarrhea
divided by the total number of people at risk. In this example, the at-risk group is those who
have eaten both ice cream and pizza. Of these 52 persons, 39 developed diarrhea.
Question 6
What is the overall attack rate in persons who did not eat ice cream?
• 30%
33%
• 35%
• 44%
• 58%
The attack rate is the number of persons with diarrhea (14 + 9) divided by the total number of
persons who did not eat ice cream (40 + 30).
Question 7
Which of the food items (or combination of items) is most likely to be the infective item(s)?
• Pizza only
Ice cream only
• Neither pizza nor ice cream
• Both pizza and ice cream
• Cannot be assumed from the data shown
Questions with Rationale
(Complete solutions and resources for the exam)
Question 1
Which of the following is a condition which may occur during the incubation period?
• Onset of clinical illness
• Receipt of infection
• Signs and symptoms of disease
Transmission of infection
• Isolation of disease carrier through quarantine
Rationale: The incubation period is defined as the interval from receipt of infection to the time
of onset of clinical illness. Accordingly, individuals may transmit infectious agents during the
incubation period as they show no signs of disease that would enable the isolation of sick
individuals by quarantine.
Question 2
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:
• Herd immunity
• All had been immunized prior to the school year
Contact was after infectious period
• Subclinical infections were not yet detected
• Disease was endemic in the class
,The disease is spread by contact with an infected individual who can transmit the agent (VZV)
to immunologically naive persons during the incubation period and for several days after onset
of clinical illness. Since the boy started school 14 days after showing signs consistent with
chicken pox, it is most likely that he was no longer infectious.
Question 3
The ability of a single person to remain free of clinical illness following exposure to an infectious
agent is known as:
• Hygiene
• Vaccination
• Herd immunity
Immunity
• Latency
Immunity is the capacity of a single individual to avoid disease susceptibility when exposed to
an infectious agent. Herd immunity is a population characteristic. For certain diseases,
individual immunity can be acquired by vaccination, but this is not true for all infectious
Question 4
Which of the following is characteristic of a single-exposure, common-vehicle outbreak?
• Long latency period before many illnesses develop
• There is an exponential increase in secondary cases following initial exposures
• Cases include only those who have been exposed to sick persons
The epidemic curve has a normal distribution when plotted against the logarithm of time
• Wide range in incubation times for sick individuals
Single-exposure, common-vehicle outbreaks involve a sudden, rapid increase in cases of disease
that are limited to persons who share a common exposure. Additionally, few secondary cases
develop among persons exposed to primary cases. A histogram of the outbreak can plot the
number of cases by time of disease onset. In single-exposure, common-vehicle outbreaks, a log
transformation of the time of disease onset will often take on the characteristic shape of a
normal distribution (i.e., a bell curve) with the median incubation time found at the peak of the
curve.
What is the diarrhea attack rate in persons who ate both ice cream and pizza?
, 39/52
• 21/70
• 39/67
• 51/67
• none of the above
The attack rate in this example is defined as the number of persons who develop diarrhea
divided by the total number of people at risk. In this example, the at-risk group is those who
have eaten both ice cream and pizza. Of these 52 persons, 39 developed diarrhea.
Question 6
What is the overall attack rate in persons who did not eat ice cream?
• 30%
33%
• 35%
• 44%
• 58%
The attack rate is the number of persons with diarrhea (14 + 9) divided by the total number of
persons who did not eat ice cream (40 + 30).
Question 7
Which of the food items (or combination of items) is most likely to be the infective item(s)?
• Pizza only
Ice cream only
• Neither pizza nor ice cream
• Both pizza and ice cream
• Cannot be assumed from the data shown
