What is Nipah virus and why is Asia on high alert?

Airports across Asia have been placed on high alert after India confirmed two cases of the deadly Nipah virus in the eastern state of West Bengal over the past month, prompting regional concerns about a potential wider outbreak.

Thailand, Nepal and Vietnam are among the countries that have begun screening airport arrivals amid fears of cross-border transmission. The Nipah virus can spread from animals to humans and carries a high fatality rate, an explainer by The Guardian notes. 

India’s health ministry confirmed that two cases have been detected in West Bengal since December but said there had been a “timely containment” of the virus. Authorities did not release details about the infected patients, citing privacy concerns, but said nearly 200 close contacts had been tested, with no additional cases identified.

What is the Nipah virus?

Nipah virus is a zoonotic disease primarily transmitted to humans from animals such as pigs and fruit bats, either through direct contact or exposure to their bodily secretions. The virus has an incubation period ranging from four to 14 days.

Early symptoms typically include high fever, nausea, vomiting and respiratory difficulties, which can progress to pneumonia. In severe cases, the infection causes acute swelling of the brain, leading to neurological symptoms such as drowsiness, confusion and seizures.

The virus is also capable of human-to-human transmission. The World Health Organization considers Nipah a high epidemic risk due to the absence of a vaccine and its exceptionally high fatality rate, estimated at between 40% and 75%, significantly higher than that of Covid-19.

History of outbreaks

Nipah virus was first identified in 1998 among pig farmers in Malaysia, where it killed more than 100 people. The virus was named after the village in which it was discovered.

Since then, outbreaks have been reported almost annually in parts of Asia, including India, the Philippines, Singapore and Malaysia. It has appeared frequently in Bangladesh, and India’s first recorded case occurred in 2001 in West Bengal, which shares a border with Bangladesh.

In Bangladesh, outbreaks have been linked to the consumption of raw date palm sap, which can become contaminated by fruit bats that commonly roost in date palm trees.

India has also experienced outbreaks in the southern state of Kerala, where at least 17 people died in 2018 and two more fatalities were reported in 2023.

Response to the latest cases

The current outbreak is notable because it marks the first detection of Nipah virus in West Bengal since 2007. Indian health authorities said: “Enhanced surveillance, laboratory testing, and field investigations were undertaken … which ensured timely containment of the cases.”

To date, no additional cases have been identified beyond the two confirmed since December.

“The situation is under constant monitoring and all necessary public health measures are in place,” the health ministry said.

Despite India’s assurances, several countries have tightened precautionary measures. Thailand, Vietnam and Indonesia have introduced enhanced screening procedures, including temperature checks and health declarations for passengers arriving from India. Myanmar has advised against nonessential travel to West Bengal, while China has strengthened disease prevention measures in its border regions.

India has pushed back against reports suggesting a surge in cases, saying such claims were “speculative and incorrect”.

By Sabina Mammadli