Several Asian countries have tightened airport screening and public health surveillance after India confirmed fresh cases of the deadly Nipah virus in the eastern state of West Bengal, raising regional vigilance against the rare but highly lethal infection.
Indian authorities confirmed two Nipah virus cases since December, pushing back against media reports that cited higher figures, calling them “speculative and incorrect”. Officials said swift containment measures had prevented further spread.
Nipah is a zoonotic virus, meaning it can be transmitted from animals to humans. It can also spread through contaminated food or via close contact between people. According to the World Health Organization (WHO), fruit bats are the virus’s natural hosts, with infections often linked to exposure to bat secretions or contaminated fruit.
The virus has a high fatality rate, estimated at between 40 and 75 per cent, and can cause a wide range of illnesses, from respiratory distress to severe neurological complications. Symptoms usually begin with sudden flu-like signs such as fever, headache and fatigue, and may include sore throat, muscle aches, vomiting, dizziness and drowsiness.
In some patients, the disease progresses to pneumonia and acute respiratory problems. The most serious complication is encephalitis, or inflammation of the brain, which typically develops three to 21 days after initial symptoms appear. The UK Health Security Agency has described encephalitis as the “hallmark” of Nipah infection, noting that it is associated with very high mortality and can leave survivors with long-term neurological problems, including persistent seizures.
The first human cases of Nipah virus were recorded between 1998 and 1999 in Malaysia and Singapore, after the virus spread from infected pigs to farm workers. About 180 people were infected in Malaysia, while 11 cases were reported in Singapore among abattoir workers handling imported pigs. No new cases have been reported in either country since.
Subsequent outbreaks have occurred mainly in western Bangladesh and parts of India, particularly in Kerala and West Bengal.
Despite its severity, experts say the risk of widespread transmission remains low. Dr Leong Hoe Nam, an infectious disease specialist at Mount Elizabeth Novena Hospital in Singapore, said Nipah is far less contagious than diseases such as COVID-19.
“The basic reproduction number for Nipah is around 0.5, meaning one infected person transmits the virus to less than one other person on average,” Dr Leong said. By comparison, measles and chicken pox have reproduction numbers of around 15, while COVID-19 and influenza range between 1.6 and 2.
He added that transmission typically requires close physical contact, placing household members and healthcare workers at higher risk.
“There is currently no proven treatment or vaccine for Nipah,” Dr Leong said, noting that care is limited to intensive supportive treatment for severe cases.
In response to the outbreak, several countries have stepped up preventive measures. Thailand began screening passengers on January 25 at three airports receiving direct flights from West Bengal, including Bangkok’s Suvarnabhumi and Don Mueang airports, as well as Phuket.
Cambodia, Jakarta and Nepal have also enhanced monitoring, while Singapore will introduce temperature screening for flights arriving from affected areas. Singapore’s Ministry of Manpower said it is stepping up surveillance of newly arrived migrant workers from South Asia.
Malaysia’s Health Minister Dzulkefly Ahmad said the country’s health security system is “robust, tested and ready”, while Vietnam has ordered stricter food safety practices and increased monitoring at borders and health facilities. China has also strengthened disease prevention measures in border regions.
Indian health authorities said 196 contacts linked to the two confirmed cases in West Bengal had been traced and all tested negative.
“The situation is under constant monitoring, and all necessary public health measures are in place,” India’s health ministry said.
Health agencies stress that the risk to tourists remains very low if standard precautions are followed, including avoiding contact with bats and sick animals, washing fruit thoroughly, and practising good hand hygiene.
