Researched by: Sara Varghese and Samreen Faridi 

Tell me more about Nipah…

The virus: It is a zoonotic virus—which means it can be transmitted from animals to humans. Nipah’s natural host is a family of bats called Pteropodidae—which can spread severe disease to various farm animals including pigs. The name Nipah comes from Sungai Nipah, a village in the Malaysian peninsula where the virus was first identified during an outbreak of encephalitis (inflammation of the brain) among pig farmers in Malaysia in 1998/99. The disease it causes is called NiV.

How it spreads: Infected bats eat fruit, or urinate or drop feces in proximity to humans or animals—who then spread it to others. So either you have direct contact with infected animals or humans—or you consume contaminated food such as fruit or palm sap. The disease has a long incubation period—as long as 45 days—so people often pass it on before they realise they are sick. It can take anywhere between 4-14 days to show symptoms.

Compared to Covid: NiV is more lethal but also less infectious. The fatality rate (percentage of infections that result in death) is anywhere between 40-75%—based on past outbreaks. That’s compared to Covid’s 1.3% average. OTOH, NiV is far, far less infectious—and requires close contact with nasal or respiratory droplets, urine, or blood. That’s unlike the coronavirus which can spread through airborne droplets. Nipah’s reproductive number—the number of people that one person can infect—is as low as 0.33. This means 10 people can at best infect three other people. For the original Wuhan virus, this number is 2-3, and it’s even higher for the Delta variant: between 5-6. 

Symptoms: NiV is a very nasty disease. It typically starts with flu-like symptoms: fever, headaches, vomiting and sore throat. But it can then progress to dizziness, drowsiness, altered consciousness and signs of encephalitis—the inflammation of the brain. Patients can develop severe respiratory problems. And in the worst cases, encephalitis and seizures will progress to coma within 24 to 48 hours.

Treatment: There are no specific drugs to treat NiV or vaccines to prevent infection. Once a person falls ill, doctors typically treat the symptoms, and offer supportive care—hoping the patient’s body will be able to fight off the virus. Since NiV is a poor person’s disease, epidemiologists say there has been little incentive to find a cure:

“There’s a market failure for protecting people from this. It’s not like treating baldness or breast cancer, where wealthy people will pay for your product. There’s no big customer here, no incentive, until it escalates.” 

Point to note: There is a version of ‘long haul’ NiV where survivors show persistent neurological effects, including personality changes. Also this: “The disease is also so deadly that many governments classify it as a bioterrorism threat and limit the laboratories that are allowed to culture and study it.” And this:

“Each year, the World Health Organization (WHO) reviews the large list of pathogens that could cause a public health emergency to decide how to prioritise their research and development funds. They focus on those that pose the greatest risk to human health, those that have epidemic potential, and those for which there are no vaccines. Nipah virus is in their top 10.”

And Nipah is only in Kerala?

Not at all. We just think so because the most recent outbreaks have taken place in the state. 

A Southeast Asian disease: Nipah outbreaks have been identified in Malaysia, Singapore, Bangladesh and India. One reason why it is more common in these countries:

“In many South-East Asian countries, the possibilities for the virus to spill over from bats to other animals and to humans are endless. Fruit bats live in trees in close proximity to markets, places of worship, schools and tourist spots. Bat guano is used as fertiliser in fields too, meaning that farmers and agricultural workers are potentially in frequent contact with the virus.”

The other reason: The popularity of date palm juice. Bats often urinate in the collection pots hung on trees: “Innocent locals would pick up a juice the next day from their street vendor, slurp away and become infected with the disease.”

The Bangladesh border: Nipah outbreaks are common in the country—and often spill over the border into India. Between 2001 and 2011, 196 people were infected in the country—of whom 150 died. Outbreaks are a regular occurrence on the ‘Nipah belt’ on the border—and research indicates that bats throughout Bangladesh carry the virus. Some scientists believe that Nipah was circulating for a long time in the country—long before it was detected in Malaysia. And one reason these cases are never identified is that people are too poor to seek help. 

Point to note: The first two outbreaks in India took place in West Bengal—transported over the border from Bangladesh. In 2001, there were 66 cases and 45 deaths. In 2007, five cases were detected and all the patients died. The third outbreak was in Kerala in 2018—when 23 cases were identified, and 17 died.

So what’s happening now?

It isn’t surprising that Nipah has popped up back in the state—since 22% of the bats are estimated to harbour the virus. But what is impressive is how quickly the disease was detected—when a 12-year old was brought into the hospital in Kozhikode. He had consumed a fruit called rambutan—likely infected with the virus:

“The patient was brought intubated from the medical college hospital on September 1 with high fever and vomiting. He had reported epilepsy at the medical college. We suspected Nipah infection as the patient was not responding to medicines and had myocarditis (inflammation of heart muscles). Hence, we sent samples to NIV Pune on September 2 itself.’’

The immediate measures: taken included the following:

• An active case search in the families, village, and areas in Malappuram district is underway. Teams are conducting door-to-door surveys. 
• Authorities have traced anyone who was in proximity to the boy in the past 12 days. 
• 251 people have been identified and quarantined—of whom 129 are health workers—which include 54 persons in the high risk category.
• As of now, 11 have displayed symptoms—but are stable.
• There is now a three kilometre containment zone around the boy’s village—and all roads leading to it have been blocked.
• A special lab has been set up to rapidly process tests in Kozhikode.
• Investigators are taking a look at half-eaten rambutan fruits and goats reared by the boy’s family to search for the source.
• The union government has rushed in a team from the National Centre for Disease Control (NCDC) to the state.

The bottomline: When a case of Nipah was detected in Kerala back in 2019, the state’s healthcare system was able to stop the outbreak in its tracks—without a single fatality. And that lightning speed response may prevent an outbreak once again. On the other hand, children are dying by the dozens in Uttar Pradesh from a “mystery illness”—which remains a mystery only because the government has neither the will nor the resources to detect and prevent the tragedy.

Reading list

Indian Express has the most details about the current outbreak. The Telegraph reports on why NiV is easier to contain than Covid. BBC News and CNN offer very good deep dives into how bats may cause the next pandemic. For more on the Kerala model: The Wire explains how Kerala successfully battled its previous Nipah epidemic in 2018, while The News Minute explains how they traced patient zero. Mint looks at how the state averted one in 2019.