Epidemic

Epidemic

Q. 1

Typhoid Mary his known in history to cause more than 1300 cases in her lifetime. This is an example of which of the following epidemic?

 A

Common source single exposure epidemic

 B

Common source continuous or repeated exposure epidemic

 C

Long term or secular trend epidemic

 D

Propagated epidemic

Q. 1

Typhoid Mary his known in history to cause more than 1300 cases in her lifetime. This is an example of which of the following epidemic?

 A

Common source single exposure epidemic

 B

Common source continuous or repeated exposure epidemic

 C

Long term or secular trend epidemic

 D

Propagated epidemic

Ans. B

Explanation:

Here the carrier, infected people over a period of time and hence there was no explosive rise in patient cases.

But over a long duration many people were affected.

So it is a Common source continuous or repeated exposure epidemic.

Ref: Park’s Textbook of Preventive Medicine, 17th Edition, Page 56.

Q. 2

All are true regarding point-source epidemic except‑

 A

All cases occur abruptly and simultaneously

 B

Children are most commonly affected

 C

Occurs within a specified period

 D

No secondary waves

Q. 2

All are true regarding point-source epidemic except‑

 A

All cases occur abruptly and simultaneously

 B

Children are most commonly affected

 C

Occurs within a specified period

 D

No secondary waves

Ans. B

Explanation:

Ans. is b i.e., Children are most commonly involved

o The main aim of descriptive epidemiology is to study the distribution of disease in time, place and person.

Time distribution

o There are three kinds of time trends or fluctuations in disease occurence :‑

A.      Short term fluctuations epidemics

B.      Secular trends or long term fluctuations

C.      Periodic fluctuation

Short term fluctuation

o The best known short – term fluctuation in the occurence of a disease is an epidemic.

o There are three major types of epidemics ‑

1) Common – source epidemics

a)       Single exposure or point source epidemics

b)       Continuous or multiple exposure epidemics

2) Propagated epidemics

3) Slow (modern) epidemics

Common source epidemics

q        As name suggests, the source of disease agent is common for all cases.

q        It is of two types.

a) Single exposure or point source epidemics

o The exposure to the disease agent is brief and essentially simultaneous —> single exposure.

  • Because disease agent enters into all exposed persons at same time —> the resultant cases all develop within one incubation period of the disease.
  • The epidemic curve rises and falls rapidly.
  • Because exposure is single (simultaneous) with no further exposure —> No secondary wave (no secondary case).
  • Epidemic tends to be explosive, there is clustering of cases within a narrow interval of time. o Point source epidemics are mostly (not always) due to exposure to an infectious agent.
  • Examples —> Food poisoning, Bhopal gas tragedy, Minamata disease in Japan, Chernobyl tragedy.

b) Continous or multiple exposure epidemics

o Exposure from the common (same) source is prolonged – continous, repeated or intermittent. o Exposure is not at the same time or place.

o For examle, a prostitute may be a common source in a gonorrhea outbreak, but since she will infect her clients over a period of time there may be no explosive rise in number of case.

  • Because disease agent enters into exposed person at different time —> outbreaks continues over more than one incubation period.

o Example –> Outbreak of legionnaire’s disease (respiratory illness) in 1976 in Philadelphia (USA).


Q. 3

Regarding point source epidemic true –

 A

Rapid rise and fall

 B

Only infectious cause

 C

Explosive

 D

a and c

Q. 3

Regarding point source epidemic true –

 A

Rapid rise and fall

 B

Only infectious cause

 C

Explosive

 D

a and c

Ans. D

Explanation:

Ans. is ‘a’ i.e., Rapid rise and fall; ‘c’ i.e., Explosive 

Quiz In Between


Q. 4

Point source epidemic tends to –

 A

Continue over one incubation period

 B

Produce multiple peaks in the epidemic curve

 C

Be explosive

 D

Tail gradually

Q. 4

Point source epidemic tends to –

 A

Continue over one incubation period

 B

Produce multiple peaks in the epidemic curve

 C

Be explosive

 D

Tail gradually

Ans. C

Explanation:

Ans. is ‘c’ i.e., Be explosive 


Q. 5

While investigating an epidemic, search for more cases is continued till what period ?

 A

Twice the incubation period of the disease since occurrence of the last case

 B

Thrice the incubation period of the disease since occurrence of the case

 C

The longest incubation period for the disease

 D

Incubation period for the disease plus two standard deviations

Q. 5

While investigating an epidemic, search for more cases is continued till what period ?

 A

Twice the incubation period of the disease since occurrence of the last case

 B

Thrice the incubation period of the disease since occurrence of the case

 C

The longest incubation period for the disease

 D

Incubation period for the disease plus two standard deviations

Ans. A

Explanation:

Ans. is ‘a’ i.e., Twice the incubation period of the disease since occurrence of the last case 


Q. 6

What is not true about point source epidemic ?

 A

Plateau phase

 B

No secondary waves

 C

Explosive epidemic

 D

Only one peak

Q. 6

What is not true about point source epidemic ?

 A

Plateau phase

 B

No secondary waves

 C

Explosive epidemic

 D

Only one peak

Ans. A

Explanation:

Ans. is ‘a’ i.e., Plateau phase 

Quiz In Between


Q. 7

Which of the following is a characteristic of a point source epidemic ?

 A

Herd immunity regulates spread of cases

 B

Person to person transmission is seen

 C

Secondary wave of cases is always seen

 D

All cases develop within one incubation period

Q. 7

Which of the following is a characteristic of a point source epidemic ?

 A

Herd immunity regulates spread of cases

 B

Person to person transmission is seen

 C

Secondary wave of cases is always seen

 D

All cases develop within one incubation period

Ans. D

Explanation:

Ans. is ‘d’ i.e., All cases develop within one incubation period 


Q. 8

First case in an epidemic is called –

 A

Index case

 B

Primary case

 C

First case

 D

None of the above

Q. 8

First case in an epidemic is called –

 A

Index case

 B

Primary case

 C

First case

 D

None of the above

Ans. B

Explanation:

Ans. is ‘b’ i.e., Primary case 


Q. 9

First step in investigating an epidemic is:

September 2005

 A

Confirmation of the epidemic

 B

Isolation

 C

Mass immunization

 D

Verification of the diagnosis

Q. 9

First step in investigating an epidemic is:

September 2005

 A

Confirmation of the epidemic

 B

Isolation

 C

Mass immunization

 D

Verification of the diagnosis

Ans. D

Explanation:

Ans. D: Verification of the diagnosis

In investigating an outbreak, speed is essential, but getting the right answer is essential, too. To satisfy both requirements, epidemiologists approach investigations systematically, using the following 10 steps:

  • Verify the diagnosis-It is the first step
  • Establish the existence of an outbreak
  • Defining the population at risk
  • Define and identify cases and their characteristics
  • Describe and orient the data in terms of time, place, and person
  • Develop hypotheses
  • Evaluate hypotheses
  • Evaluation of ecological factors
  • Further investigation of populato at risk
  • Writing report/ Communicate findings

The steps are presented here in conceptual order. In practice, however, several may be done at the same time, or they may actor be done in a different order. For example, control measures should be implemented as soon as the source and mode of transmission are known, which may be early or late in any particular outbreak investigation.

Quiz In Between


Q. 10

First step in epidemic done by an epidemiologist‑

 A

Identity the cases

 B

Confirm the diagnosis

 C

Identify the prone people

 D

Identify the causative factors

Q. 10

First step in epidemic done by an epidemiologist‑

 A

Identity the cases

 B

Confirm the diagnosis

 C

Identify the prone people

 D

Identify the causative factors

Ans. B

Explanation:

Ans. is ‘b’ i.e., Confirmation of diagnosis

Steps for Investigation of Epidemic :

  • Verification of diagnosis :
  • Is the first step in investigation of an epidemic’
  • Confirmation of existence of an epidemic:
  • Compare with disease frequencies during same period in previous years
  • Epidemic threshold: An arbitrary limit of ‘2 standard errors from the endemic occurrence’

Defining the population at risk:

  • Obtaining the map of the area
  • Calculation of ‘appropriate denominator of population at risk’

Rapid search for all cases and their characteristics:

  • Medical survey
  • Epidemiological case sheet
  • Searching for more cases: Search for new cases is carried out everyday, till the area is declared free of epidemic; this period is usually taken as ‘twice the incubation period of the disease since the occurrence of last case’

Data analysis:

  • Formulation of hypothesis
  • Testing of hypothesis
  • Evaluation of ecological factors
  • Further investigation of population at risk
  • Writing the report

Q. 11

Not true about propagated epidemics ‑

 A

Gradual rise

 B

Gradual fall

 C

Person to person transmission

 D

No secondary wave

Q. 11

Not true about propagated epidemics ‑

 A

Gradual rise

 B

Gradual fall

 C

Person to person transmission

 D

No secondary wave

Ans. D

Explanation:

Ans. is ‘d’ i.e., No secondary wave

Quiz In Between



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