Nipah virus

Scientific summary

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What is it?

Nipah virus (NiV) belongs to the Paramyxoviridae family of viruses, genus Henipavirus, alongside Hendra virus. Nipah is a zoonotic disease, meaning it passes from animals to humans.

The natural hosts of the virus are fruit bats (also known as flying foxes) of the genus Pteropus. Nipah virus can be spread to people from infected bats, infected pigs or infected people.

Where does it occur?

Nipah virus was first identified in 1999 during an outbreak of illness affecting pig farmers and others having close contact with pigs in Malaysia and Singapore. Over 100 human deaths were reported, and over a million pigs were killed in the effort to stop the outbreak. No cases of person-to-person spread were reported. In 2001, there was an outbreak of Nipah virus in people in Bangladesh, and a separate outbreak in a hospital in India. In both countries, person-to-person transmission occurred. Since then, Bangladesh has suffered outbreaks nearly every year – with over 300 confirmed cases occurring there from 2001 to 2015.

India has also occasionally reported cases and experienced an outbreak in the southern State of Kerala earlier this year. A total of 19 Nipah virus cases, including 17 deaths, were reported from Kerala State: 18 of the cases were laboratory-confirmed and the deceased index case was suspected to have NiV but could not be tested. Those who died included a nurse who had been caring for a patient ill with Nipah virus disease. More than 2500 contacts of Nipah patients were monitored by the state surveillance system and a 24-hour helpline took queries from the community. By mid-June, the Kerala government and the Union Health Ministry announced that the outbreak had been contained.

So far, Nipah outbreaks have been confined to South and Southeast Asia, but Pteropus bats are found in a large geographical area across the globe covering a population of more than 2 billion people. A spread of the virus among these bat populations could therefore put a huge number of people worldwide at risk of zoonotic infection. Furthermore, as the virus is capable of person-to-person spread, in theory a Nipah-infected individual could bring the virus even to regions where Pteropus bats do not live and infect others in those regions. Thus, Nipah virus has the biological potential to be a truly global threat.

What does it do?

Nipah virus infection can cause severe, rapidly progressive illness that affects the respiratory system and the central nervous system, including inflammation of the brain (encephalitis). Symptoms begin between 5 and 14 days after infection, and include fever, altered mental state, cough and respiratory problems.

How do we currently prevent infections?

People are advised to avoid contact with ill pigs and bats in countries where Nipah virus is known to occur. They are also advised to avoid drinking raw date palm sap, which can be infected with bodily fluids from bats.

There are currently no vaccines or specific therapeutics against Nipah virus approved for use in humans.