Nipah virus — DTM&H MCQ

Correct answer: D — Nipah virus infection

D, Nipah virus infection, is correct because raw date palm sap consumption in Bangladesh is the classic epidemiological link to Nipah outbreaks, and the subsequent illness in carers reflects human to human spread via respiratory secretions and body fluids, a recognised feature of Bangladeshi Nipah clusters. Fresh sap is contaminated by Pteropus fruit bats (the wildlife reservoir) that feed and urinate on sap collection pots overnight, and drinking unpasteurised sap is the primary route of bat to human transmission. The virus then causes a febrile illness with cough progressing to encephalitis, and secondary cases in family members or healthcare workers occur through close contact, exactly as described in the vignette. This triad of raw sap exposure, encephalitis, and clustering in carers is the key discriminator that points specifically to Nipah rather than any other endemic encephalitis. Why the other options are wrong: A, Avian influenza: causes severe respiratory illness after poultry exposure, not date palm sap, and does not typically produce encephalitis or efficient household clustering in this pattern. B, Lassa fever: is a West African rodent-borne haemorrhagic fever transmitted via rodent excreta or contaminated food, with no association with Bangladesh or date palm sap, and it presents with haemorrhagic features rather than encephalitis. C, Rabies: follows an animal bite (usually dog) with a long incubation and hydrophobia/agitation, not sap ingestion, and does not spread from person to person through casual caregiving contact. E, Japanese encephalitis: is mosquito-borne, linked to rural rice-growing and pig-rearing areas, and does not cause secondary cases among carers since humans are dead-end hosts with no person-to-person transmission. Key point: Encephalitis after raw date palm sap ingestion in Bangladesh, with secondary cases in close contacts, is the classic exam pattern for Nipah virus infection.

Reference: UK Health Security Agency, 'Nipah virus: what is it, where is it found and how does it spread?', UKHSA blog, 2026, https://ukhsa.blog.gov.uk/2026/01/27/nipah-virus-what-is-it-where-is-it-found-and-how-does-it-spread/