NR503
NR503
Week8 Final
Student exam;
Consult Questions with Rationale
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?
NR503
Week8 Final
Student exam;
Consult Questions with Rationale
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?
