Question
Mode of transmission, clinical presentation and laboratory diagnosis of Nipah virus infection (2+2+2)
Answer
Nipah virus infection
Mode of transmission: Nipah virus (genus Henipavirus, family Paramyxoviridae) is primarily a zoonotic infection, with fruit bats (Pteropodid/flying foxes) serving as the natural reservoir. Transmission to humans occurs via: consumption of raw date palm sap or fruit contaminated with bat saliva/urine/excreta (the predominant route in outbreaks in the Indian subcontinent, including Kerala); contact with infected intermediate hosts (e.g., pigs, as occurred in the original Malaysian outbreak); and direct human-to-human transmission via contact with infected respiratory secretions/body fluids (particularly significant in healthcare settings, given documented nosocomial spread).
Clinical presentation: presents with fever, headache, myalgia, vomiting, and altered sensorium, progressing rapidly to acute encephalitis with reduced consciousness, seizures, and, in severe cases, coma; respiratory symptoms/acute respiratory distress syndrome can also occur. Case fatality rate is very high (up to 40-75% in various outbreaks, notably including Kerala outbreaks), making it a priority pathogen for public health surveillance.
Laboratory diagnosis:
- RT-PCR — detection of viral RNA from throat/nasal swab, CSF, urine, or blood; the primary confirmatory diagnostic test, requiring high-containment (BSL-4) laboratory handling given the organism’s high pathogenicity and lack of approved vaccine/specific treatment.
- Serology (ELISA) — detection of IgM (acute infection) and IgG antibody.
- Virus isolation — possible but requires BSL-4 containment facilities, not routinely performed outside specialized reference laboratories.
- Given the high biosafety risk, testing is typically centralized to designated national/reference laboratories (e.g., National Institute of Virology, India), and strict infection-control precautions (including barrier nursing and PPE) are essential when managing suspected cases, given the risk of nosocomial transmission.