A recent virus outbreak in India is stoking new fears of a pandemic across Asia, leading several countries to reinstate airport screenings reminiscent of COVID-19 measures in an effort to contain its spread.

Heightened vigilance at airports follows the confirmation of five Nipah virus cases in India’s West Bengal region. This rare but highly lethal virus, transmitted by bats, poses a significant threat as it can infect both pigs and humans.

Health authorities are particularly concerned about Nipah virus because of its zoonotic nature, enabling transmission from animals to humans and, in some instances, between people. Compounding the threat is the current absence of an approved vaccine or targeted drug treatment for the virus.

The current outbreak has been traced back to a private hospital in West Bengal, where it was reported that at least five healthcare workers contracted the virus earlier this month.

In a precautionary move, officials have quarantined approximately 110 individuals who had contact with the infected patients, aiming to prevent further spread.

A doctor, a nurse and another staff member at the hospital tested positive after the first two cases were detected in a male and female nurse from the same district.

Narayan Swaroop Nigam, the principal secretary of the Department of Health and Family in Bengal, said one of the nurses is in critical condition after they both developed high fevers and respiratory issues between New Year’s Eve and January 2.

The critically ill nurse, who is now in a coma, is believed to have contracted the infection while treating a patient suffering from severe respiratory problems. 

That patient died before tests for Nipah virus could be carried out.

In response, Thailand’s ministry of public health has implemented health screening for passengers at major airports arriving from West Bengal.

Travellers are being assessed for fever and other Nipah virus symptoms including headache, sore throat, vomiting and muscle pain, and are being issued health ‘beware’ cards advising what to do if they become ill.

Phuket International Airport is also undergoing increased cleaning due to its direct flight links with West Bengal, despite no cases being reported in Thailand.

Local media reports have stated that travellers with a high fever or other symptoms consistent with Nipah virus may be taken to quarantine facilities.

Nepal has raised alert levels at Tribhuvan International Airport in Kathmandu and land crossings bordering India, while Taiwan has said it is planning to list Nipah virus as a Category 5 notifiable disease – the highest classification for serious emerging infections – which would require immediate reporting and special control measures if cases occur.

Taiwan’s Centres for Disease Control said it is maintaining its Level 2 ‘yellow’ travel alert for Kerala state in southwestern India, advising travellers to exercise caution.

So far, no cases have been reported outside India, and there is no sign of Nipah spreading to the US or elsewhere in North America. But the response shows just how seriously authorities are treating the risk.

Nipah has a fatality rate of between 40 and 75 per cent, according to the World Health Organization, from complications such as respiratory failure and swelling of the brain. 

Nipah remains rare, but experts warn it has the potential to cause devastating illness when it strikes.

Here’s what it is, how it spreads – and how worried we should be about the outbreak escalating.

What is Nipah virus? 

Nipah is a zoonotic infection, meaning it can pass from animals to humans – most notably linked to fruit bats, and in some outbreaks pigs.

It’s a virus that worries health officials because it can hit fast and hard, causing anything from no symptoms at all to a sudden, severe illness that attacks the lungs and the brain.

In milder cases, people may only feel flu-like symptoms – but in severe cases it can trigger acute respiratory distress, seizures and encephalitis, a dangerous swelling of the brain that can be fatal.

Another reason it sets alarm bells ringing is that it has been shown to spread person-to-person, particularly among family members and caregivers, making strict infection control crucial when cases are detected.

Health authorities monitor Nipah due to its outbreak potential – and because its death rate in confirmed cases is unusually high. 

Why are authorities suddenly screening for it at airports?

Airport checks have been stepped up after cases were detected in West Bengal, with the outbreak linked to healthcare settings where viruses can spread quickly if not contained.

Thailand has started screening arrivals at international airports receiving flights from the region, while Nepal has introduced checks at Kathmandu airport and at land border points with India. 

Taiwan has also proposed classifying Nipah as a high-risk emerging infection under its disease control system.

While measures like these can look dramatic, officials are essentially trying to spot illness early and block any chance of infections slipping across borders.

Airport staff said to be looking for obvious signs of illness, such as a high temperature, are flagging up passengers who have recently travelled from an affected area and reporting symptoms that could fit an early Nipah infection.

Health declaration forms, mandatory temperature checks and full body heat scanners are the main method of doing this.  

Anyone who appears unwell can then be pulled aside for further medical assessment, with health authorities able to trace contacts more quickly if an infection is suspected.

How does it spread?

Nipah can spread from animals to humans, and it can also be transmitted through contaminated food or direct person-to-person contact.

During the first recognised outbreak in Malaysia in the late 1990s, which also affected Singapore, most human infections were linked to contact with sick pigs or their contaminated tissue, with transmission thought to have occurred through unprotected exposure to secretions from infected animals.

In later outbreaks in Bangladesh and India, researchers believe a key source of infection was consumption of fruit or fruit products contaminated by fruit bats, including raw date palm juice tainted with infected urine or saliva.

Human-to-human transmission has also been reported, particularly among family members and caregivers of infected patients. 

Preliminary investigations suggest the healthcare workers in India caught the deadly virus while treating a patient with severe respiratory symptoms who died before testing could be carried out, according to sources at the hospital.

‘The most likely source of infection is a patient who had been admitted to the same hospital previously. That individual is being treated as the suspected index case, and investigated,’ a health official involved surveillance efforts told The Telegraph.  

Health authorities in Taiwan are now considering listing the virus as a Category 5 disease – a rare or emerging infection with major public health risks, that require immediate reporting and special control measures.

What are the symptoms?

Nipah can begin with symptoms that look like a bad flu or stomach bug, including fever, headaches, muscle aches, vomiting and a sore throat.

In some people, it escalates into something far more serious, with dizziness, drowsiness, confusion and neurological signs that point to acute encephalitis – dangerous inflammation of the brain. Severe cases can involve seizures and rapid deterioration, sometimes progressing to coma within 24 to 48 hours.

Some patients also develop atypical pneumonia and severe breathing problems, including acute respiratory distress.

The incubation period is usually four to 14 days, but it can sometimes be much longer. In rare instances, an incubation period of up to 45 days has been reported.

How deadly is it?

Nipah is known for its high fatality rate. The estimated case fatality rate is 40 to 75 per cent, though this varies between outbreaks depending on how quickly patients are diagnosed and how strong clinical care and surveillance are in affected areas. 

In the worst cases, Nipah can be a rapid and brutal illness because it can cause severe inflammation of the brain (encephalitis) and acute respiratory failure.

Case descriptions from past outbreaks suggest some patients deteriorate from what looks like a standard viral illness – fever, aches, vomiting – into confusion, extreme drowsiness and seizures, before slipping into coma within 24 to 48 hours. 

Others develop severe breathing problems, including pneumonia and acute respiratory distress, which can be fatal without intensive supportive care.

However many people who survive make a full recovery – but the virus is feared because severe cases can worsen dramatically, and some survivors are left with long-term neurological damage. 

There have also been reports of relapse in a small number of cases.

Is there a vaccine or treatment?

There are currently no approved vaccines or drugs that specifically target Nipah virus infection.

Instead, doctors rely on intensive supportive care, treating the most dangerous respiratory and neurological complications as they arise.