What you need to know about the virus that has a 70% mortality rate in India

The southern Indian state of Kerala has shut down some schools and offices this week as authorities race to contain the spread of the deadly Nipah virus, after two recent deaths.

Scientists first identified the Nipah virus in 1998 during an outbreak among pig farmers in Malaysia and Singapore, Reuters reported. The outbreak had a significant economic impact as more than a million pigs were culled to control the disease.

Although there have been no other outbreaks of Nipah virus in Malaysia and Singapore since 1999, cases have since been reported almost annually in some parts of Asia – mainly Bangladesh and India.

To date, there is no vaccine to prevent or cure the virus once infected. The disease has a mortality rate of up to about 70%. Treatment is usually supportive care to treat symptoms.

The World Health Organization (WHO) says that early symptoms include fever, respiratory distress, headache and vomiting. Encephalitis and seizures can also occur in severe cases, leading to coma within 24 to 48 hours.

WHO lists Nipah virus as a research and development pathogen with pandemic potential.

Medical workers bury the body of a patient who died from the Nipah virus, in Kozhikode, Kerala state, southern India. (Photo: AP).

Authorities have stepped up contact tracing efforts, identifying, isolating and testing those who may have come into contact with the boy. Veena George, Kerala's health minister, said that as of September 6, 188 people who came into contact with the boy had been identified, of whom 20 were at high risk of infection, mostly family members. All have been placed under strict quarantine or hospitalized.

On September 6, two health workers who came into contact with a patient with symptoms of Nipah virus infection were hospitalized and had blood samples taken for testing.

Authorities have sealed off an area within a radius of about 3km of the boy's home and are screening all nearby districts of Kerala for symptoms. Neighbouring Tamil Nadu is also on high alert for any suspected cases of fever.

This is the second time in three years that a Nipah virus outbreak has been reported in Kerala, which is also experiencing a high rate of Covid-19 cases. About 68% of the 40,000 new Covid-19 cases reported every day in India are in Kerala.

What is Nipah virus?

Nipah is a virus that is transmitted from animals to humans . Transmission usually occurs through direct contact with animals or through the consumption of contaminated food. However, cases of Nipah virus transmission from person to person have also been documented.

Fruit bats of the family Pteropodidae, commonly known as flying foxes , are natural carriers of Nipah virus. They can transmit the virus to other animals including pigs, dogs, cats, goats, horses and sheep.

People infected with Nipah virus typically experience symptoms such as fever and headache for three days to two weeks. They may then develop a cough, sore throat, and respiratory problems. The disease can progress rapidly and cause brain swelling, leading to drowsiness, confusion, coma, and death.

There is currently no treatment or vaccine for Nipah virus and patients receive only supportive medical care.

According to the World Health Organization (WHO), up to 75% of Nipah virus infections are fatal. Meanwhile, the mortality rate for SARS-CoV-2 is about 2% of cases. About 20% of survivors may experience lasting neurological symptoms such as seizures and personality changes.

A researcher catches bats to collect samples for Nipah virus research in Shuvarampur area of ​​Faridpur district, Bangladesh. (Photo: Reuters).

Is Nipah virus a new threat?

Nipah virus was first detected in Malaysia in 1999 during an outbreak among pig farmers. Since then, there have been several outbreaks in South and Southeast Asia, resulting in more than 260 deaths.

An outbreak in Bangladesh in 2004 was linked to people consuming Nipah-infected date palm sap from infected fruit bats. The last outbreak in India in 2018 in Kerala state killed 17 of 18 people infected. The infections were linked to fruit bats found dead in a family's well.

Nipah virus is considered less contagious than SARS-CoV-2 , but its mortality rate is much higher. Its longer incubation period of up to 45 days and ability to infect a wide range of animals make Nipah a significant concern for epidemiologists trying to predict and prevent the next pandemic.

Veasna Duong, a virologist at the Pasteur Institute in Phnom Penh, Cambodia, has studied human-bat contact in the region and says the close proximity of humans and bats in markets and other crowded places across Asia poses a serious risk of infection.

Veasna Duong told the BBC that, in some cases, the Nipah virus could mutate and pose a risk of causing a future pandemic.

'We have observed fruit bats in Cambodia and Thailand, in markets, places of worship, schools and tourist sites like Angkor Wat. There are a lot of bats there. Every year, Angkor Wat receives about 2.6 million tourists. That is 2.6 million opportunities for Nipah virus to jump from bats to humans every year in just one place ,' said expert Veasna Duong.

Scientists warn that warming climates and human destruction of natural habitats for animals such as fruit bats in Asia will create opportunities for viruses transmitted from animals to emerge.

In its note on Nipah virus, the WHO warns of 'the risk of the virus being transmitted to other countries through fruit or fruit products, such as date juice, contaminated with urine or saliva from infected fruit bats'. The WHO also recommends that transmission of the virus can be prevented by thoroughly washing and peeling fruit before consumption, and that fruit that shows signs of bat bites should be discarded.