Student Consult
Chapter 2-4
Which of the following is a condition which may occur during the incubation period?
Transmission of infection
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.
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
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.
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 diseases.
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
Chapter 2-4
Which of the following is a condition which may occur during the incubation period?
Transmission of infection
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.
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
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.
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 diseases.
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
