The Indian state of Kerala is battling its fourth outbreak of the Nipah virus since 2018. Two people have died and nearly 800 people have been tested over the last 48 hours in the state’s district of Kozhikode.

Two adults and a child are in hospital for observation after testing positive.

It is listed by the World Health Organization (WHO) among the those deemed to pose the greatest public health risk due to their epidemic potential and a lack of sufficient countermeasures. 

Here’s a look at what is known about the virus — and whether people in Canada should be worried. 

What is Nipah virus?

Nipah is a zoonotic virus, meaning it can be transmitted between animals and humans but can also spread through contaminated food or from human to human.  It kills 40 to 75 per cent of people who become infected, according to the health organization.

Nipah was first identified in 1999 in pig farmers in Malaysia and Singapore. Most of those cases result from farmers coming into direct contact with their sick pigs or with contaminated pig tissues. About 300 people were confirmed infected and 100 people died. 

There has not been another known outbreak in either country since, according to the U.S. Centers for Disease Control (CDC). 

In 2001, Nipah was first identified in Bangladesh. Since then, the country has experienced yearly outbreaks, with cases generally occurring between December and May, according to WHO.

It’s believed the infections in Bangladesh are caused by people consuming fruit or fruit products — like raw date palm juice or date palm sap — that has become contaminated by the urine or saliva of the fruit bats that feed on the sap. 

According to WHO, the fruit bat is considered a natural host of the virus. Fruit bats from Kerala tested positive for the Nipah virus during the state’s first outbreak in 2018, which killed 21 of the 23 people infected.

Subsequent outbreaks in Kerala, in 2019 and 2021, killed two people.

In the face of the current outbreak in the state, samples of bat urine, animal droppings and half-eaten fruit have been collected from the village of Maruthonkara, where the first victim of this outbreak lived. The community is located beside a 120-hectare forest that is home to several bat species. 

“We are testing human beings … and at the same time, experts are collecting fluid samples from forested areas that could be the hotspot for the spread,” Veena George, Kerala’s health minister, told Reuters. 

About 800 people have already been tested in the past week, with at least 77 deemed as being at high risk for infection, according to George.