Two cases lethal Nipah virus in India have prompted authorities in Thailand and Malaysia to step up screening at airports to prevent the spread of the infection.

But what is Nipah virus, and how worried should people be? Here are some answers.

India’s health ministry said on Tuesday that two cases of Nipah had been detected since December and that all identified contacts had been quarantined and tested. The ministry did not release details of the patients, but said 196 contacts had been found and all tested negative.

“The situation is under constant monitoring and all necessary public health measures are being taken,” the Ministry said.

There have been no reported cases of the virus outside India, but several Asian countries have introduced or stepped up screening measures at airports as a precaution.

What is Nipah virus?

Nipah is a rare viral infection that mainly spreads from infected animals, mainly fruit bats, to humans. It can be asymptomatic, but it is often very dangerous, with mortality rate from 40 to 75 percent, depending on the local health system’s capacity for detection and management, says the World Health Organization.

However, while it can also spread from person to person, it doesn’t do so easily, and outbreaks are usually small and fairly contained, according to experts and European Center for Disease Prevention and Control. Candidate vaccines are in development, although none have yet been approved.

How common is that?

Nipah was the first it was identified in Malaysia in 1999. Since then, there have been smaller outbreaks almost every year, mostly in Bangladesh. India has also seen sporadic outbreaks.

By December, a total of 750 cases had been reported and 415 patients had died, according to the Coalition for Epidemic Preparedness Innovations, a group that monitors emerging disease threats and funds the development of medical tools to protect against them.

How does it spread?

When it was first identified in Malaysia, Nipah spread larthrough direct contact with sick pigs or contaminated tissues. Since then, it has spread more often from contact with what scientists say is its natural host: fruit bats.

Specifically, consumption of fruit or fruit products – such as raw date palm juice – that contain the urine or saliva of infected fruit bats is the most likely source of infection, the WHO says. Human-to-human spread has been established, mainly after close contact between a sick patient and his family or caregiver.

What are the symptoms?

Initial symptomoms of Nipah, such such as fever, headaches and muscle aches, are not specific and can be mistaken for other illnesses. This can be followed by neurological signs suggestive of acute encephalitis or inflammation of the brain, and some people have serious respiratory problems.

WATCH | Nipah outbreak in India 2018.

The rare viral disease Nipah is re-emerging in India

Ten people there died after contracting the Nipah virus, a disease believed to be spread by fruit bats and other animals.

Seizures occur in severe cases, progressing to coma in a few days. Most people who recover make a full recovery, but some have long-term neurological problems.

How worried should we be?

While Nipah is adan angry disease with a high death rate, has not yet shown signs of becoming more transmissible between humans or spreading easily around the world, scientists say.

However, according to the WHO, it remains a significant public health problem, especially in countries where outbreaks are more frequent. It can also lead to the mass destruction of domestic animals, such as pigs, which are susceptible to the virus.

Scientists say it is unlikely to spread globally — but they also point out that screening at the airport could be ineffective because the virus has a long incubation period.

What vaccines or treatments are there?

There are currently no approved vaccines or treatments for Nipah, although a number of candidates are undergoing testing, including one developed by scientists from the University of Oxford involved in the development of one of the vaccines against COVID-19.

Their Nipah vaccine usis the same technology and began phase 2 testing in Bangladesh in December in collaboration with the International Center for Diarrheal Disease Research, Bangladesh, and with funding from the Emergency Preparedness Innovation Coalition.