Question 1

Which of the following best defines an outbreak?&#10;A)The diagnosis of several cases of disease in the same geographic region&#10;B)The diagnosis of several cases in the same week&#10;C)The number of cases observed in an area is twice that normally reported in the same time period&#10;D)The number of cases observed in an area is ten times that normally reported in the same time period&#10;E)The number of cases observed in an area is clearly higher than would normally be expected in the same time period

Accepted Answer

An outbreak or epidemic is defined as an increase in disease 'clearly' above
the level expected.While both A and B might also represent an outbreak we do not
have any comparison data to know whether the numbers observed are usual or not.
The outbreak may extend to several communities or countries and can last from days to
years.An outbreak can refer to a disease that has not previously be known in that
country or alternatively has been absent from the population for a long time and has
reoccurred after years of absence.

Question 2

Clusters of disease can be challenging to investigate because:&#10;A)Cases of disease can occur close together (geographically or in time) just by chance&#10;B)They are usually caused by environmental hazards&#10;C)The exposure and disease usually occur very close together&#10;D)The disease usually only has a single cause&#10;E)All of the above&#10;F)Noneoftheabove

Accepted Answer

Clusters are challenging to investigate because cases of disease will cluster
together by chance and it can be very hard to know whether a cluster really exists.In
many cases the disease in question will not have a single cause (D) and there may be a
very long latency between exposure to the postulated cause and disease onset (C).

Question 3

In the investigation of an epidemic the most appropriate measure to describe the frequency of occurrence of illness is the:&#10;A)Prevalence&#10;B)Incidence rate&#10;C)Case&#8208;fatality rate&#10;D)Attack rate&#10;E)Mortality rate

Accepted Answer

The attack rate is an incidence proportion or cumulative incidence; it
measures the proportion of people that develop an outcome of interest and is
particularly useful for short time periods.Prevalence (A) measures the proportion of the
population who have disease at a point in time; it tells us nothing about who is newly
affected.The incidence rate (B) tells us how quickly cases are developing in a
population, usually per year.It is less useful when short‐term measures are required
such as during an outbreak.The case‐fatality rate (C) tells us what proportion of people
with a disease will die from it and the mortality rate (E) tells us how quickly people in
the population are dying but neither tell us anything about how many are developing
the disease.

Question 4

If the latent period for an infection is longer than the incubation period then:&#10;A)People may pass on the infection before they become sick&#10;B)People will become sick before they can pass on the infection&#10;C)An epidemic is likely to occur&#10;D)The disease is likely to be endemic in the population&#10;E)A pandemic is likely to occur

Accepted Answer

If the latent period (the interval between infection and when someone can
transmit the infection to someone else) is longer than the incubation period (the interval
between infection and the onset of clinical disease) then people will be sick before they
can pass on the infection.This means that an epidemic (C) or pandemic (E) are unlikely to
occur.This tells us nothing about whether a disease is endemic in the population (D).

Question 5

At what point in an outbreak investigation should you start to initiate control and prevention activities?&#10;A)After you have confirmed the cause of the outbreak&#10;B)After developing hypotheses as to what might have caused the outbreak&#10;C)After verifying the diagnosis&#10;D)After confirming that an outbreak exists&#10;E)As soon as possible&#10;F)Afterwritingyourfinalreport

Accepted Answer

Control measures should be introduced as early as possible during an
outbreak investigation and as soon as the mode of transmission is identified - an
example would be recalling a contaminated product from supermarkets.Control
activities will often be conducted in parallel with the other steps of the investigation.

Question 6

If you were investigating an outbreak, in what order would you normally conduct the steps below?
Analysedatabytime,placeandperson
Conductacase‐controlstudy
Generatehypotheses
Conductactivesurveillanceforadditionalcases
Verifythediagnosis
Confirmthatthenumberofcasesexceedstheexpectednumber

A)1‐2‐3‐4‐5‐6
B)5‐6‐4‐1‐2‐3
C)6‐5‐3‐1‐2‐4
D)6‐5‐4‐1‐3‐2

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Accepted Answer

Early steps include confirming that the number of cases exceeds the
expected number (i.e.that the outbreak exists), verifying the diagnosis.The next steps
are to identify any additional cases and analyse the data by time, place, and person to
generate hypotheses about the potential cause of the outbreak that can then be tested
by conducting, for example, a case‐control study.

Question 7

In the investigation of an epidemic of a fatal disease such as SARS, the most appropriate measure to describe the frequency of death from the disease is the:&#10;A)Mortality rate&#10;B)Case&#8208;fatality rate&#10;C)Attack rate&#10;D)Standardised mortality ratio&#10;E)Incidence rate

Accepted Answer

The case‐fatality rate (also called the case‐fatality ratio) is the proportion of
people with a given disease/condition who die from it in a given period.It is a common
measure of the short‐term severity of an acute disease.The mortality rate (A) also
measures the rate at which people die from a disease but it is usually calculated over a
period of one year and so is less appropriate for an epidemic of a rapidly fatal disease.It
also tells us nothing about how many people are getting the disease and so nothing
about how fatal it is.The attack rate (C) tells us how quickly people are developing the
disease but nothing about how many are dying from it.The standardised mortality ratio
(D) tells us how much likely someone is to die of disease in one population compared to
a reference population while the incidence rate (E) measures the rate at which people in
the population are getting the disease.

Question 8

A spot map is particularly useful for displaying: (Select all that apply)&#10;A)The location of exposure of each case&#10;B)The location of the local medical facilities&#10;C)The residence of each case&#10;D)Incidence rates of disease by area&#10;E)The place of employment of each case

Accepted Answer

A spot map is useful for pinpointing the geographic location of
exposures, residences, employment sites, and the like.Each case is represented by a spot
on the map.Spot maps are not used to display rates (D).

Question 9

Which of the following best describes the factors that influence the spread of an infectious disease?&#10;A)Agent, host, environment&#10;B)Agent, host, transmission&#10;C)Agent, host, transmission, environment&#10;D)Agent, source, transmission&#10;E)Agent, infectivity, susceptibility

Accepted Answer

The agent itself, the susceptibility of the host, the route of transmission and the
environment can all influence the spread of an infectious disease.A traditional model of
infectious disease causation is sometimes known as the 'epidemiological triad'.This model
comprises an agent (e.g.a pathogen like salmonella), a host (e.g.human) and an
environment (e.g.a closed environment such as a restaurant) that brings the host and
agent together.This triad is centred around a 'vector' (e.g.a food containing the
salmonella) that enables the transmission of the agent to the host.

Question 10

Which of the following can be the reservoir for an infectious disease? (Select all that apply)&#10;A)Another human&#10;B)An animal&#10;C)An insect&#10;D)Food&#10;E)The air&#10;F)Alloftheabove

Accepted Answer

The reservoir can be another human (e.g.tuberculosis), animal
(where the disease may be present but may not harm the animal, e.g.rabies in bats) or
non?living things (like water or soil, e.g.hepatitis A).

Deck 13: Outbreaks, Epidemics and Clusters