Confirmed cases of Nipah virus (NiV) in India’s West Bengal state have prompted heightened health screenings across Asia, raising concerns about the potential for wider regional spread of the deadly virus.
The World Health Organization (WHO) has reported the newly confirmed cases, triggering a response from several Asian nations to tighten airport health protocols. Nipah virus periodically resurfaces in South and Southeast Asia, drawing global attention due to its exceptionally high fatality rate, which can exceed 50% in many outbreaks, according to the WHO and the U.S. Centers for Disease Control and Prevention (CDC).
NiV is a zoonotic virus, typically transmitted from animals to humans, but can also spread through contaminated food or direct person-to-person contact. Fruit bats of the Pteropus family are considered the natural host, and are present across Asia and Australia, though outbreaks are currently concentrated in specific regions.
The virus was first identified in 1998 during an outbreak among pig farmers in Malaysia, and subsequently in Singapore in 1999 following the importation of infected pigs. Since 2001, outbreaks have been detected in India and Bangladesh, with Bangladesh experiencing almost annual occurrences. India reports periodic outbreaks, including the latest in 2026, and a previous outbreak in the state of Kerala in 2018 highlighted the risk of human-to-human transmission, particularly within healthcare settings.
Transmission to humans most often occurs through close contact with infected animals or consumption of contaminated food. A well-documented example involves raw date palm sap, consumed in parts of India and Bangladesh, which can be contaminated by bat saliva or urine. Fruits partially eaten by bats also pose a potential contamination risk, as does contact with infected livestock.
Although not easily spread person-to-person, human-to-human transmission has been confirmed, particularly in family clusters and hospital environments. The 2018 Kerala outbreak saw several healthcare workers infected after caring for patients without proper diagnosis, demonstrating the risk of secondary transmission. Epidemiological data suggests a basic reproduction number (R₀) generally below 1, limiting sustained community spread, but localized outbreaks remain possible.
Symptoms of NiV infection vary, ranging from asymptomatic cases to severe illness. Initial symptoms, appearing 4-14 days after infection, include fever, headache, muscle aches, vomiting, and sore throat. Severe cases can progress rapidly to acute encephalitis, seizures, altered consciousness, and coma. Respiratory complications, such as pneumonia or acute respiratory distress syndrome, are also possible. The reported fatality rate ranges from 40% to 75%, with approximately 20% of survivors experiencing persistent neurological sequelae.
Diagnosis relies on molecular and serological techniques requiring high-security laboratories. Authorities in affected countries have strengthened surveillance, particularly in hospitals, to rapidly identify suspected cases and limit secondary transmission.
Currently, there are no approved vaccines or antiviral treatments for NiV infection. Patient care focuses on supportive measures. Though, research is underway, including candidate vaccines, such as a vector-adenovirus vaccine developed by the University of Oxford, currently in early-stage clinical trials in at-risk regions. Monoclonal antibodies are also being investigated as potential prophylactic or post-exposure treatments.
The WHO has included Nipah virus on its R&D Blueprint for priority pathogens, recognizing the severity of the disease and the gaps in medical countermeasures. The recent outbreaks have prompted some countries to enhance screening of travelers from affected areas, though the risk of importation is not currently considered high.
