There are currently no approved vaccines or treatments, although a number of candidates are being tested.
Two cases of the deadly Nipah virus in India have prompted authorities in Thailand and Malaysia to step up checks at airports to prevent the spread of the infection.
Pakistan has also ordered strict and enhanced health surveillance at all entry points following regional alerts.
But what is Nipah virus and how worried should people be?
What is Nipah virus?
Nipah is a rare viral infection that spreads largely from infected animals, primarily fruit bats, to humans. It can be asymptomatic but it is often very dangerous, with a case fatality rate of 40 to 75%, depending on the detection and management capacity of the local health system, specifies the World Health Organization (WHO).
However, while it can also spread from person to person, it doesn’t happen easily and outbreaks are usually small and fairly contained, according to experts and the European Center for Disease Prevention and Control. Vaccine candidates are being developed, but none have yet been approved.
Is this common?
Nipah was first identified in Malaysia in 1999. Since then, small outbreaks have occurred almost every year, mainly in Bangladesh. India also experiences sporadic outbreaks.
According to the Coalition for Epidemic Preparedness Innovations (CEPI), a group that tracks emerging disease threats and funds the development of medical tools to protect against them, as of December, a total of 750 cases had been recorded, and 415 of the patients had died. Reuters traced the spread of Nipah in a 2023 series, BatLands.
Learn more: Pakistan strengthens border surveillance against Nipah virus
How is it spread?
When first identified in Malaysia, Nipah was spread largely through direct contact with diseased pigs or contaminated tissues. Since then, it has spread more often through contact with what scientists consider its natural host: fruit bats. Specifically, consumption of fruit or fruit products – such as raw date palm juice – containing urine or saliva from infected fruit bats was the most likely source of infection, according to the WHO.
Human-to-human spread has been noted, primarily after close contact between a sick patient and their family or caregivers.
What are the symptoms?
Early symptoms of Nipah such as fever, headache and muscle pain are nonspecific and can be confused with other illnesses. These can then be followed by neurological signs indicating acute encephalitis or inflammation of the brain, and some people experience serious breathing problems.
Seizures occur in severe cases, progressing to coma within a few days. Most people who improve make a full recovery, but some suffer long-term neurological problems.
How worried should we be?
Although Nipah is a dangerous disease with a high mortality rate, it has not yet shown signs of human-to-human transmission or spreading easily around the world, scientists say. However, it remains a significant public health problem, according to the WHO, particularly in countries where outbreaks are more common.
It can also lead to the mass culling of farm animals, such as pigs, which are susceptible to the virus. Scientists, however, say it is unlikely to spread globally – and also point out that screening at airports could be ineffective because the virus has a long incubation period.
What vaccines or treatments are available?
There is currently no approved vaccine or treatment for Nipah, although a number of candidates are being tested, including one developed by the University of Oxford scientists involved in the development of one of the Covid-19 vaccines.
Their Nipah vaccine uses the same technology and began phase II testing in Bangladesh in December in collaboration with the Bangladesh International Center for Diarrheal Disease Research and with funding from CEPI.
