NR-503-WEEK-8
Question 1
Which of the following is a condition which may occur during the incubation period?
That's correct!
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 wouldenable 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 theboy returned to school, none of his classmates had
been infected by VZV. The main reason was:
That's correct!
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 hewas no longer infectious.
Question 3
The ability of a single person to remain free of clinical illness following exposure
to aninfectious agent is known as:
That's correct!
Immunity is the capacity of a single individual to avoid disease
susceptibilitywhen 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.
,Question 4
Which of the following is characteristic of a single-exposure, common-vehicle outbreak?
That's correct!
Single-exposure, common-vehicle outbreaks involve a sudden, rapid
increase incases 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
characteristicshape 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?
That's correct!
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 52persons, 39 developed diarrhea.
Question 6
What is the overall attack rate in persons who did not eat ice cream?
That's correct!
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).
,Which of the food items (or combination of items) is most likely to be the
infectiveitem(s)?
That's correct!
Among persons eating ice cream, over 70% developed diarrhea regardless
of their pizza consumption (39/52 and 11/15). Among both groups of
persons whodid not eat ice cream, each attack rate was equal to or less
than 35% (14/40and 9/30).
Question 8
Which of the following reasons can explain why a person who did not
consume theinfective food item got sick?
That's correct!
Without knowledge as to the specific agent in this instance, it is also likely
that itcan be spread by direct contact with infected persons. Since diarrhea
is a general disease symptom, it is possible that several infectious agents
may be present at this meal or others eaten during the same time period.
Further, information regarding food consumption may have been collected
long after the disease episode. This may have led persons to incorrectly
remember the foodsthat they consumed.
Question 9
An outbreak of gastroenteritis occurred at a boarding school with a
student enrollmentof 846. 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 numberreporting illnesses consistent with the described
symptoms and onset time. Calculate the attack rate among all students
at the boarding school.
That's correct!
The answer is found by dividing the total number of cases (57) by the
totalnumber of students (846). This equals 6.7%.
Question 10
An outbreak of gastroenteritis occurred at a boarding school with a
student enrollmentof 846. 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 numberreporting illnesses consistent with the described
symptoms and onset time. Calculate the attack rates for boys and girls
separately.
That's correct!
For boys, the attack rate includes all cases (40 + 3) divided by the total
numberof students who are boys (380 + 46). The attack rate is 10.1%.
For girls, the attack rate includes all cases (12 + 2) divided by the total
numberof students who are girls (343 + 77). The attack rate is 3.3%.
Question 11
Question 1
Which of the following is a condition which may occur during the incubation period?
That's correct!
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 wouldenable 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 theboy returned to school, none of his classmates had
been infected by VZV. The main reason was:
That's correct!
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 hewas no longer infectious.
Question 3
The ability of a single person to remain free of clinical illness following exposure
to aninfectious agent is known as:
That's correct!
Immunity is the capacity of a single individual to avoid disease
susceptibilitywhen 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.
,Question 4
Which of the following is characteristic of a single-exposure, common-vehicle outbreak?
That's correct!
Single-exposure, common-vehicle outbreaks involve a sudden, rapid
increase incases 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
characteristicshape 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?
That's correct!
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 52persons, 39 developed diarrhea.
Question 6
What is the overall attack rate in persons who did not eat ice cream?
That's correct!
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).
,Which of the food items (or combination of items) is most likely to be the
infectiveitem(s)?
That's correct!
Among persons eating ice cream, over 70% developed diarrhea regardless
of their pizza consumption (39/52 and 11/15). Among both groups of
persons whodid not eat ice cream, each attack rate was equal to or less
than 35% (14/40and 9/30).
Question 8
Which of the following reasons can explain why a person who did not
consume theinfective food item got sick?
That's correct!
Without knowledge as to the specific agent in this instance, it is also likely
that itcan be spread by direct contact with infected persons. Since diarrhea
is a general disease symptom, it is possible that several infectious agents
may be present at this meal or others eaten during the same time period.
Further, information regarding food consumption may have been collected
long after the disease episode. This may have led persons to incorrectly
remember the foodsthat they consumed.
Question 9
An outbreak of gastroenteritis occurred at a boarding school with a
student enrollmentof 846. 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 numberreporting illnesses consistent with the described
symptoms and onset time. Calculate the attack rate among all students
at the boarding school.
That's correct!
The answer is found by dividing the total number of cases (57) by the
totalnumber of students (846). This equals 6.7%.
Question 10
An outbreak of gastroenteritis occurred at a boarding school with a
student enrollmentof 846. 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 numberreporting illnesses consistent with the described
symptoms and onset time. Calculate the attack rates for boys and girls
separately.
That's correct!
For boys, the attack rate includes all cases (40 + 3) divided by the total
numberof students who are boys (380 + 46). The attack rate is 10.1%.
For girls, the attack rate includes all cases (12 + 2) divided by the total
numberof students who are girls (343 + 77). The attack rate is 3.3%.
Question 11
