The Nipah virus, a zoonotic disease primarily carried by fruit bats and occasionally transmitted through animals such as pigs, is known for causing severe fever and brain inflammation. While it has a high fatality rate ranging between 40 and 75 percent, medical experts emphasize that it does not spread easily from person to person and usually requires close or prolonged contact.

The two confirmed cases were detected in the eastern Indian state of West Bengal in late December, with both patients identified as healthcare workers. They are currently receiving treatment at a local hospital, and authorities report that their condition is being closely monitored under strict medical supervision.

Indian health officials have traced nearly 200 contacts linked to the infected individuals, with all testing negative and showing no symptoms so far. Enhanced surveillance, laboratory testing, and field investigations were carried out promptly, helping to contain the situation and reduce the risk of wider transmission.

Following reports of the cases, neighboring and regional countries including Singapore, Thailand, Malaysia, Hong Kong, and Nepal have tightened border health measures. These steps are precautionary and focus mainly on temperature screening, health declarations, and monitoring of passengers arriving from regions linked to the cases.

Singapore has announced temperature checks at its main airport for selected flights arriving from affected areas in India. The country’s health authorities are also coordinating with international counterparts to better understand the situation and strengthen global information sharing related to genome sequencing and outbreak monitoring.

Hong Kong has implemented enhanced health screening at its international airport, including temperature checks at arrival gates for passengers traveling from India. Airport authorities are working closely with health departments to ensure swift identification of any suspected cases.

Thailand has introduced designated parking bays for aircraft arriving from areas reporting Nipah infections, along with mandatory health declaration forms for passengers before immigration clearance. Malaysia has similarly increased preparedness by strengthening health screening at international entry points, particularly for travelers from higher-risk countries.

China has stated that no Nipah cases have been detected domestically but has acknowledged the potential risk of imported infections. Nepal, which shares an open and busy border with India, has declared a high alert and intensified screening of travelers entering the country.

Medical experts note that Nipah outbreaks are not new to the region. The virus was first identified more than 25 years ago during an outbreak among pig farmers in Malaysia and Singapore, though scientists believe it has circulated in fruit bat populations for thousands of years.

The World Health Organization classifies Nipah as a priority pathogen due to the lack of licensed vaccines or treatments, its high fatality rate, and concerns that future mutations could increase transmissibility. Several vaccines are currently under development but remain in trial stages.

India has reported sporadic Nipah cases in the past, particularly in the southern state of Kerala, which is considered one of the world’s highest-risk regions for the virus. The recent cases in West Bengal are the state’s first in nearly two decades, marking a significant but contained public health event.

Two adults and a child were still infected in hospital, and more than 700 people were being tested for the virus, spread via contact with the bodily fluids of infected bats, pigs or people, a state health official said.

The state government on Wednesday evening said at least 706 people, including 153 health workers, were undergoing tests to check the spread of the virus. Results were awaited.

“More people could be tested …I solation facilities will be provided,” Pinarayi Vijayan, chief minister of Kerala, said in a statement. He asked people to avoid public gatherings in the Kozhikode district for the next 10 days.

Two infected people have died since Aug. 30 in Kerala’s fourth outbreak of the virus since 2018, forcing authorities to declare containment zones in at least eight Kozhikode villages.

“We are focusing on tracing contacts of infected persons early and isolating anyone with symptoms,” state Health Minister Veena George told reporters.

She said the virus detected in Kerala was the same as one found earlier in Bangladesh, a strain that spreads from human to human with a high mortality rate but has a history of being less infectious.

“Public movement has been restricted in parts of the state to contain the medical crisis,” she said, adding that state epidemiologists were using antivirals and monoclonal antibodies to treat three people infected, including a medical worker.

Strict isolation rules have been adopted, with medical staff being quarantined after contact with the infected.

The first victim was a small landholder growing bananas and areca nuts in the Kozhikode village of Maruthonkara, said a government official who retraced the movement of that person to track down all people he could have interacted with and the places he visited before his health started to deteriorate.

The victim’s daughter and brother-in-law, both infected, are in an isolation ward, while other family members and neighbours are being tested.

The second death followed contact in hospital with the first victim, an initial investigation has shown, but the two were not related, added the official, who sought anonymity as he was not authorised to talk to the media.

The Nipah virus was first identified in 1999 during an outbreak of illness among pig farmers and others in close contact with the animals in Malaysia and Singapore.

Outbreaks are sporadic and previous infections in South Asia have occurred when people drank date-palm sap contaminated with bat excreta.

The first victim’s native village, Maruthonkara, is situated near a 300-acre forest that is home to several bat species. During the 2018 Nipah outbreak, fruit bats from the same area tested positive for the virus.

In Kerala’s first Nipah outbreak, 21 of the 23 people infected died. Outbreaks in 2019 and 2021 killed two people.

Neighbouring Tamil Nadu state announced that travellers coming from Kerala would be subjected to medical tests and those with flu symptoms would be isolated.

A Reuters investigation in May identified parts of Kerala as among the places most at risk globally for outbreaks of bat viruses, especially as extensive deforestation and urbanisation have brought people and wildlife into closer contact.

One adult and one child are still infected and in hospital, and more than 130 people have so far been tested for the virus, which is transmitted to humans through direct contact with the bodily fluids of infected bats, pigs or other people, an official from Kerala’s health ministry said.

One person died this month while another death occurred on Aug. 30, while two more people from the same family, including one child, were the ones infected and in hospital.

Authorities declared containment zones in seven villages of the Kozhikode district, closing down schools, banks and other institutions.

Three teams from the federal government including the National Virology Institute were scheduled to arrive in Kerala on Wednesday for further testing, said the official who did not want to be quoted as he was not authorised to talk to the media.

The deadly brain-damaging Nipah virus was first identified in 1999 during an outbreak of illness affecting pig farmers and others in close contact with pigs in Malaysia and Singapore.

This is the fourth Nipah outbreak in Kerala since 2018. The first and worst outbreak began with a 26-year-old man who went to hospital with a fever and cough that spread to family members and other patients before it was diagnosed as Nipah.

Twenty one of the 23 infected people died then. In 2019 and 2021, Nipah claimed two more lives.

A Reuters investigation published in May identified parts of Kerala as among the places most at risk globally for outbreaks of bat viruses. Extensive deforestation and urbanisation have brought people and wildlife into close contact.