Outbreak of Nipah virus sparks alarm across Southeast Asia

Sammy Westfall

Airports in Southeast Asia are on alert this week after the confirmation of an outbreak of Nipah virus, which has no known cure, in West Bengal, India.

Thailand implemented health screening checkpoints for passengers from West Bengal on Sunday and Taiwan’s Centers for Disease Control announced plans to list the disease as a Category 5 threat, local media reported.

Two cases have been confirmed, the Indian Health Ministry said in a statement Tuesday. Nearly 200 close contacts have been monitored and tested, the statement said.

There are outbreaks of Nipah - which has a fatality rate of 40 to 70%, according to the Centers for Disease Control and Prevention - nearly every year in South Asia. Still, there is low global awareness of the virus. Amid the ongoing outbreak, no breakout cases have been reported beyond India.

What is Nipah virus, and how is it transmitted?

Nipah virus is zoonotic, transmitted to people from animals. People can contract it from direct contact with infected animals, primarily flying fox bats and pigs, as well as their contaminated tissues or secretions.

One can be infected by consuming food, such as fruit, contaminated by the animals in question. Outbreaks in Bangladesh have been linked to raw date palm juice made with sap contaminated by fruit bats.

Once the virus spreads to humans, it can spread from person to person through close contact.

For the outbreak in India, as in previous instances and in other viral outbreaks, enhanced surveillance in the region and travel screening will be crucial to controlling the spread, experts say.

How contagious is Nipah virus?

Nipah virus was discovered in Malaysia in 1999, when a major outbreak among pig farmers killed more than 100 people. It is highly contagious among pigs.

Since then, Nipah outbreaks have occurred almost annually in Asia, particularly in Bangladesh and India. Over the past several years, routine outbreaks have occurred in Bangladesh in a “predictable season pattern” between December and April, according to research in a November paper in the Journal of Infection and Public Health. The authors linked that pattern to the peak harvesting season for raw date palm sap - a cultural delicacy and tradition. Fruit bats often live in date trees.

Outbreaks have also occurred in Malaysia, the Philippines and Singapore.

This month’s outbreak is notable because it is West Bengal’s first confirmed outbreak since 2007. “This represents a return of Nipah to this area after a long gap, which is concerning from a surveillance standpoint,” said Lauren Sauer, an associate professor at the University of Nebraska Medical Center.

This month, the governments of India and West Bengal “initiated prompt and comprehensive public health measures in accordance with established protocols,” the Health Ministry said. They undertook “enhanced surveillance, laboratory testing, and field investigations,” which “ensured timely containment of the cases.” No additional Nipah cases have been detected since the original two cases, the ministry said.

When scientists were racing to find the origins of the coronavirus pandemic in 2020, the first Nipah outbreak was viewed as a case study in zoonotic disease spillover from animals to humans. (A zoonotic origin for the coronavirus that led to the pandemic has not been proved but remains a leading explanation.)

What are the symptoms of Nipah virus?

The sickness begins within days of infection, with symptoms including fever, headache, cough, muscle pain and difficulty breathing. As the infection progresses, patients may experience neurological symptoms such as brain swelling, which can be fatal.

Those who survive encephalitis, or brain inflammation, can recover but sometimes face lifelong consequences, including seizure disorders.

How is Nipah virus treated?

According to the CDC, about 40 to 70% of people who contract Nipah virus die.

There are no licensed treatments for Nipah, according to the CDC. There are also no vaccines available.

The World Health Organization in 2018 identified Nipah as a priority pathogen in urgent need of accelerated research and development targeting the virus. Awareness of Nipah virus remains low, experts say.

There are promising vaccines in various trials, as well as recent advancements in monoclonal antibody treatments as well, Sauer said.

Because there are no drugs known to prevent or treat the disease, the best way to prevent infection is awareness of risk factors, the WHO says. That includes steps to decrease bat access to date palm sap collection sites and boiling any collected juice. The WHO advises that farmers consider proximity to bats when establishing new pig farms in the vulnerable region.

Treatment is limited to care that is “mostly supportive and requires high-quality, resource-intensive bedside management,” Sauer said.