Communicable diseases: chickenpox infectivity: practice question

A PSM question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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PSM · Communicable diseases: chickenpox infectivity

Sample item

A child develops chickenpox rash on day 0. Infectiousness of chickenpox generally extends from:

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

D. 1 to 2 days before the rash until about 5 days after the first vesicles

A patient is infectious from 1 to 2 days before the rash until about 5 days after appearance of the first crop, or until all lesions have crusted. Isolation until crusting is advised.

Option by option

  • A. Only 10 days after rash onset

    Infectivity does not begin 10 days after rash.

  • B. After all scabs have fallen off

    Scabs are not infectious, and spread ceases after crusting.

  • C. Only during the incubation period

    Infectiousness begins just before the rash and not for the whole incubation period.

  • D. 1 to 2 days before the rash until about 5 days after the first vesicles (correct)

    Correct. This is the standard infectious period.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this PSM question

What is the answer to this PSM question?

The best answer is D, 1 to 2 days before the rash until about 5 days after the first vesicles. A patient is infectious from 1 to 2 days before the rash until about 5 days after appearance of the first crop, or until all lesions have crusted.

Why is "Only 10 days after rash onset" not the answer?

Infectivity does not begin 10 days after rash.

Why is "After all scabs have fallen off" not the answer?

Scabs are not infectious, and spread ceases after crusting.

Why is "Only during the incubation period" not the answer?

Infectiousness begins just before the rash and not for the whole incubation period.

What concept does this question test?

It tests Communicable diseases: chickenpox infectivity in PSM. Isolation until crusting is advised.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Communicable diseases: chickenpox infectivity?

Practise biostatistics with small calculations until sensitivity, predictive values and risk measures are automatic. Then use the flashcards and the other PSM questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.