Nipah virus encephalitis — DTM&H MCQ
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Correct answer: E — Nipah virus
B) Nipah virus is correct. Recurrent seasonal encephalitis clusters in Bangladesh linked to date palm sap harvesting and Pteropus fruit bats is the classic epidemiological signature of Nipah virus, which is transmitted when bats contaminate raw sap with saliva, urine or excreta during nocturnal feeding, with subsequent human consumption of the sap. UKHSA notes that human outbreaks of Nipah virus have only been identified in South and South-East Asia, and that Bangladesh has had cases occurring almost annually since 2001, closely tied to the cold-season sap harvest. The reservoir host is confirmed as Pteropus fruit bats, and infection can also spread person to person via close contact, particularly with caregivers, which explains household clustering. High case fatality (commonly 40 to 75 percent) and encephalitic presentation without a specific antiviral or licensed vaccine further fit the described outbreak pattern. Why the other options are wrong: A. Japanese encephalitis virus: transmitted by Culex mosquitoes in rice-growing and pig-rearing areas, not linked to fruit bats or date palm sap; seasonality follows monsoon mosquito breeding, not sap harvest. D. Rabies virus: causes encephalitis after bite or scratch exposure to a rabid mammal (commonly dogs), with a long incubation and hydrophobia/hypersalivation picture, not clustering around sap consumption. C. Eastern equine encephalitis virus: a mosquito-borne alphavirus confined to the Americas, with no bat reservoir or link to Bangladesh or date palm sap. B. Chandipura virus: a sandfly-borne vesiculovirus reported in rural India causing paediatric encephalitis, but it lacks the bat reservoir and date palm sap transmission route described here. Key point: Encephalitis clusters in Bangladesh during the date palm sap season with Pteropus bat involvement is pathognomonic for Nipah virus, transmitted via bat-contaminated raw sap and secondarily person to person.
Reference: UK Health Security Agency (UKHSA), 'Nipah virus: what is it, where is it found and how does it spread?', UKHSA blog, 27 January 2026, https://ukhsa.blog.gov.uk/2026/01/27/nipah-virus-what-is-it-where-is-it-found-and-how-does-it-spread/