Virology: severe dengue pathogenesis: 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: severe dengue pathogenesis

Sample item

A 7-year-old who had dengue two years earlier now develops a second dengue illness and on day 4 shows plasma leakage with pleural effusion and shock. What best explains the severity?

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

The answer and the reasoning

B. Antibody-dependent enhancement from non-neutralising cross-reactive antibodies to a different serotype

Infection with one dengue serotype gives lifelong immunity to that serotype but only transient protection against the others. In a later infection with a different serotype, cross-reactive non-neutralising antibodies form complexes that enhance entry into Fc-receptor-bearing monocytes, raising viral load and cytokine release. The resulting capillary leak causes dengue shock.

Option by option

  • A. Direct neurotoxin production by the virus

    Dengue severity arises from vascular leak and not from a neurotoxin.

  • B. Antibody-dependent enhancement from non-neutralising cross-reactive antibodies to a different serotype (correct)

    Correct. Antibody-dependent enhancement increases infection of monocytes in a heterologous second infection.

  • C. Complete protection from the first infection against all serotypes

    Cross-protection between serotypes is only temporary and cannot explain a more severe illness.

  • D. Waning immunity against the same serotype only

    Waning immunity against the same serotype would not cause worse disease in a second, different serotype.

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 Microbiology question

What is the answer to this Microbiology question?

The best answer is B, Antibody-dependent enhancement from non-neutralising cross-reactive antibodies to a different serotype. Infection with one dengue serotype gives lifelong immunity to that serotype but only transient protection against the others.

Why is "Direct neurotoxin production by the virus" not the answer?

Dengue severity arises from vascular leak and not from a neurotoxin.

Why is "Complete protection from the first infection against all serotypes" not the answer?

Cross-protection between serotypes is only temporary and cannot explain a more severe illness.

Why is "Waning immunity against the same serotype only" not the answer?

Waning immunity against the same serotype would not cause worse disease in a second, different serotype.

What concept does this question test?

It tests Virology: severe dengue pathogenesis in Microbiology. In a later infection with a different serotype, cross-reactive non-neutralising antibodies form complexes that enhance entry into Fc-receptor-bearing monocytes, raising viral load and cytokine release. The resulting capillary leak causes dengue shock.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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: severe dengue pathogenesis?

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.