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Polio acute flaccid paralysis surveillance — DTM&H MCQ

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HardEpidemiology, outbreak investigation and public healthPolio acute flaccid paralysis surveillanceDTM&H

A 4-year-old unimmunised child in a border district develops acute flaccid paralysis without sensory loss. The public health team is assessing possible poliomyelitis. What is the most appropriate investigation?

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Correct answer: D — Two stool specimens for poliovirus testing collected at least 24 hours apart

The correct answer is D, two stool specimens for poliovirus testing collected at least 24 hours apart. Acute flaccid paralysis (AFP) in an unimmunised child in a border area is a classic presentation of poliomyelitis, and because poliovirus shedding in stool is intermittent, UKHSA and WHO AFP surveillance protocols require two adequate stool samples (each at least 2g), collected 24 to 48 hours apart and within 14 days of paralysis onset, sent to a reference virology laboratory. Sensory sparing with asymmetric lower motor neurone weakness further supports anterior horn cell (poliovirus) pathology rather than a peripheral neuropathy. Stool culture and PCR remain the gold standard for confirming poliovirus infection and distinguishing wild-type from vaccine-derived strains, which is essential for outbreak response. Why the other options are wrong: E. Serum Widal test: this detects antibodies to Salmonella Typhi in enteric fever, entirely unrelated to poliovirus diagnosis and irrelevant to AFP surveillance. A. Urine microscopy for ova: this looks for helminth or schistosome eggs and has no role in diagnosing a flaccid paralysis illness caused by poliovirus. C. Single throat swab after 6 weeks: a single specimen is inadequate under AFP protocols, and pharyngeal poliovirus shedding is brief and unreliable compared with faecal shedding, making a swab taken weeks later virtually useless. B. Thick blood film alone: this diagnoses malaria parasitaemia, not poliovirus, and blood is not the recommended specimen type for confirming poliomyelitis. Key point: Confirming poliomyelitis in AFP surveillance requires two stool specimens collected at least 24 to 48 hours apart because poliovirus shedding in faeces is intermittent and stool remains the most sensitive specimen.

Reference: UKHSA, 'How to report a case of acute flaccid paralysis or acute flaccid myelitis', GOV.UK, https://www.gov.uk/government/publications/acute-flaccid-paralysis-investigating-and-reporting-a-case/how-to-report-a-case-of-acute-flaccid-paralysis-or-acute-flaccid-myelitis