An outbreak of the Nipah virus in the Indian state of West Bengal is raising concern in parts of Asia, leading some airports to implement precautionary health screenings.
So far, five confirmed infections, including among doctors and nurses, have led to a quarantine of 100 people and the hospitalization of others at various medical facilities in Kolkata, according to the Times of India.
Three Thai airports that receive flights from West Bengal have started screening passengers on arrival. Nepal has also begun screening travellers at the Kathmandu airport and land border crossings with India, the BBC reported.
India’s health ministry says 196 people known to have been in contact with the infected individuals have tested negative, according to the outlet.
What is Nipah virus?
Nipah virus, which can be deadly, is transmitted through several pathways, including from animals to humans — primarily through fruit bats — via contaminated food, or directly between humans and can cause anything from asymptomatic infection to acute respiratory illness and fatal encephalitis, the World Health Organization (WHO) says.
Human‑to‑human transmission occurs through close contact with the bodily fluids of an infected person.
Although the Nipah virus has caused only a few known outbreaks in Asia, it infects a wide range of animals and causes severe disease and death in people, making it a public health concern, according to the WHO.
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Infected people generally develop flu-like symptoms such as fever, headaches, muscle pain, vomiting and a sore throat.
Some may experience respiratory issues, including shortness of breath, coughing, and, in more severe cases, pneumonia. This can be accompanied by dizziness, drowsiness and altered consciousness, which may indicate a more complex neurological infection.
The most serious symptoms affecting the central nervous system include seizures, coma and the inability to breathe.
The incubation period is believed to range from four to 14 days, but the WHO has reported an incubation period of up to 45 days.
How deadly is the virus?
Nipah virus has a death rate ranging from 45 to 75 per cent, and there is no vaccine or medical treatment available for animals or humans.
In December 2025, researchers at the University of Oxford, in partnership with the International Centre for Diarrhoeal Disease Research, Bangladesh, launched the world’s first phase two clinical trial of a Nipah virus vaccine involving 306 healthy participants aged 18 to 55.
Most people who survive acute encephalitis, an inflammation of the brain tissue, make a full recovery, though the WHO has reported long-term neurologic conditions in survivors.
Some may also develop meningitis.
Approximately 20 per cent of patients who recover from Nipah virus are left with residual neurological symptoms, such as seizure disorders, and may experience personality changes. A small number of people who recover relapse subsequently or develop delayed-onset encephalitis.
The main course of treatment for humans is supportive care. The virus is described by WHO as a “priority disease” with an “urgent need for accelerated research and development.”
In 2018, at least three people in southern India died after becoming infected with the virus. They were all from the same family.
Where are the outbreaks?
Nipah was first identified during a 1999 outbreak in Malaysia. Since then, outbreaks have been reported in parts of South Asia, including Singapore, as well as in northeast India and Bangladesh. Nipah virus has never been reported or found in Canada.
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