Nipah Virus Mode of Transmission
Nipah virus transmits to humans primarily through three pathways: direct contact with infected fruit bats (Pteropus species) or their contaminated secretions, contact with infected intermediate animal hosts (particularly pigs, cattle, and goats), and person-to-person transmission which occurs in approximately 50% of cases. 1, 2
Primary Transmission Routes
Bat-to-Human Transmission
- Consumption of contaminated date palm sap is the most common pathway in Bangladesh and India, where fruit bats contaminate raw sap with saliva or urine during feeding 2, 3
- Direct exposure occurs through shared food sources with Pteropus fruit bats or contact with bat habitats 4
- Inhalation of infectious aerosolized saliva or excreta from bats can transmit the virus 1
Animal-to-Human Transmission
- Pig-to-human transmission was the dominant route in the 1999 Malaysia outbreak, where direct contact with infected pigs caused disease in pig farmers and abattoir workers 1
- Domestic animals including cattle, pigs, and goats become infected through consumption of food contaminated with bat saliva or urine, then transmit to humans 2, 3
- Infected animals shed virus in saliva, urine, and feces, creating multiple exposure pathways 5
Person-to-Person Transmission
- Human-to-human transmission occurs in approximately 50% of recognized cases, making healthcare workers extremely high-risk during outbreaks 1, 4
- Transmission occurs through direct contact with infected patients' saliva, respiratory secretions, and other body fluids 2, 3
- Nosocomial transmission is well-documented, with viable virus found on healthcare workers' mobile phones and hospital equipment 1
Specific Exposure Mechanisms
Inhalation Route
- Infectious aerosolized saliva or excreta represent the primary mechanism of viral entry 1
- Aerosols can be generated from freshly shed material or secondary aerosols from dried excreta 5
Direct Contact Routes
- Introduction of contaminated material into broken skin or conjunctivae can cause infection 5, 1
- Rodent bites have been documented to transmit related hantaviruses, suggesting similar potential for Nipah virus 5
- Ingestion of contaminated food or water is a possible but less well-documented route 5
Critical Infection Control Implications
Airborne precautions with N-95 respirators, gowns, aprons, and face shields are mandatory for all suspected or confirmed cases because of the high rate of person-to-person transmission 1, 4
Common Pitfalls
- Do not underestimate nosocomial transmission risk—viable virus persists on surfaces and equipment, requiring rigorous decontamination protocols 1
- Avoid non-invasive ventilation or high-flow nasal oxygen in uncontrolled settings due to aerosolization risk that increases staff exposure 4
- Healthcare workers must maintain strict precautions even during brief patient encounters, as transmission can occur after only minutes of exposure 5
Geographic and Epidemiologic Context
- Endemic regions include South and Southeast Asia, particularly Bangladesh, India, Malaysia, Singapore, and the Philippines 4, 6
- Different outbreak patterns exist: Malaysia experienced primarily pig-mediated transmission, while Bangladesh and India see predominantly bat-to-human and human-to-human transmission 2, 3
- The virus does not require arthropod vectors for transmission 5