Virology: poliovirus surveillance: practice question

A Microbiology 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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Microbiology · Virology: poliovirus surveillance

Sample item

A 3-year-old child develops acute flaccid paralysis of the left leg with fever two days earlier and no sensory loss. Under the national polio surveillance programme, which specimen collection is appropriate?

AA single throat swab collected within 24 hours of onsetBCerebrospinal fluid collected only after 60 days of paralysisCTwo stool samples collected at least 24 hours apart within 14 days of onset of paralysisDA single serum sample for IgM collected after 6 weeks

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

The answer and the reasoning

C. Two stool samples collected at least 24 hours apart within 14 days of onset of paralysis

Poliovirus is shed in the faeces for weeks, so surveillance of acute flaccid paralysis relies on stool testing in a polio laboratory. Two adequate stool specimens are collected 24 to 48 hours apart, within 14 days of onset, and sent in a reverse cold chain. Virus isolation with intratypic differentiation then separates wild, vaccine-derived and Sabin-like strains.

Option by option

A. A single throat swab collected within 24 hours of onset
Throat shedding is brief and is not the standard specimen for acute flaccid paralysis surveillance.
B. Cerebrospinal fluid collected only after 60 days of paralysis
Cerebrospinal fluid is not the surveillance specimen and virus is rarely recoverable from it, so waiting 60 days would miss shedding.
C. Two stool samples collected at least 24 hours apart within 14 days of onset of paralysis (correct)
Correct. Paired stool samples collected early give the best chance of isolating poliovirus.
D. A single serum sample for IgM collected after 6 weeks
Serology is not used for case classification because the vaccine also produces antibodies.

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.

Questions about this Microbiology question

What is the answer to this Microbiology question?

The best answer is C, Two stool samples collected at least 24 hours apart within 14 days of onset of paralysis. Poliovirus is shed in the faeces for weeks, so surveillance of acute flaccid paralysis relies on stool testing in a polio laboratory.

Why is "A single throat swab collected within 24 hours of onset" not the answer?

Throat shedding is brief and is not the standard specimen for acute flaccid paralysis surveillance.

Why is "Cerebrospinal fluid collected only after 60 days of paralysis" not the answer?

Cerebrospinal fluid is not the surveillance specimen and virus is rarely recoverable from it, so waiting 60 days would miss shedding.

Why is "A single serum sample for IgM collected after 6 weeks" not the answer?

Serology is not used for case classification because the vaccine also produces antibodies.

What concept does this question test?

It tests Virology: poliovirus surveillance in Microbiology. Two adequate stool specimens are collected 24 to 48 hours apart, within 14 days of onset, and sent in a reverse cold chain. Virus isolation with intratypic differentiation then separates wild, vaccine-derived and Sabin-like strains.

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 Virology: poliovirus surveillance?

Make a one-line identity card for each organism: shape and stain, defining test, toxin, disease and drug. Then use the flashcards and the other Microbiology 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.