Another Nipah outbreak in India: What do we know about this virus and how to stop it?

A field researcher holds a male bat that was trapped in an overhead net as part of an effort to find out how the animals pass Nipah virus to humans. The animal will be tested for the virus, examined and ultimately released. Fatima Tuj Johora for NPR hide caption

toggle caption Fatima Tuj Johora for NPR

A field researcher holds a male bat that was trapped in an overhead net as part of an effort to find out how the animals pass Nipah virus to humans. The animal will be tested for the virus, examined and ultimately released.

Fatima Tuj Johora for NPR

The Southern Indian state of Kerala is now battling another deadly outbreak of the Nipah virus, its fourth since 2018. Authorities were alerted to the outbreak after two deaths attributed to the virus. A 49-year-old man named Mohammed Ali, who lived in the village of Maruthonkara, died on August 30, and 40-year-old Mangalatt Haris, who lived in the town of Ayanchery, died on September 11.

On September 13, test results confirmed that both men had died of Nipah. Authorities tested for the virus from routine nose swabs. A combination of flu-like and neurological symptoms — headache, fever, cough, acute respiratory distress and seizures — alerted them to test for the virus.

The virus, first identified among pig farmers in Malaysia in 1999, likely jumped to humans at that time from infected pigs. But there was no human-human transmission noted during the Malaysian outbreaks, says Dr. Thekkumkar Surendran Anish, associate professor for community medicine at the Government Medical College at Manjeri, Kerala, who is leading the state's surveillance team and who spoke to NPR about the situation.

On the morning of September 15, Anish encountered yet another case — a 39-year-old man who'd been attending to a patient in the adjacent bed when Mohammed Ali was hospitalized. So far, in addition to the two deaths, Kerala has confirmed six active cases of Nipah.

Kerala has a wide variety of bat species; tests of some fruit bats in 2018 showed that they . Samples of bat urine and half-eaten fruit from Maruthonkara, the village in Kozhikode, where the first victim lived, and authorities are testing bats in the area for the virus too.

, especially monitoring anyone with a fever as well as the 950 people who were in contact with the two deceased men. The state's .

"There's no rationale for masking up, since the Nipah virus does not spread through the air," says epidemiologist Raman Kutty, research director at the Amala Cancer Institute in Thrissur, Kerala. "Health authorities are just being very cautious," he says.

They've also asked the public to be vigilant for such symptoms as headache, disorientation, fever, cough and seizures. Neighboring states of Karnataka and Tamil Nadu as well.

There is no vaccine nor cure for Nipah yet, and supportive care is all that patients can be given.

"The virus has an incubation period of 14-21 days," says Anish. "Judging from the time of the secondary infections, we're still in the middle of this outbreak," he says. And there's at least one piece of the puzzle that authorities still don't know — How the patient Ali contracted Nipah in the first place.

Editor's note: For more on Nipah, here is an feature we published earlier this year:

It's dusk in central Bangladesh, in a community within the district of Faridpur. A 50-year-old man sits outside his home beside a rice paddy. His name is Khokon. A fiery beard, dyed a bright orange, rings his chin.

He says the procession of disease and death all started in the spring of 2004. "So the first one was the mother-in-law of my elder brother. She was really sick," Khokon says. "She had been sick for some time. Then she died. We took her to the grave. Then my father got sick."

Khokon stares off into the distance as he explains that his father was a spiritual leader in the community. When he became ill, many came to pay their respects and offer their prayers. "Just 12 days after, my father died," he says. "Suddenly, he was no more."

. "Some people who were transporting the patients to the hospital were also getting sick."

Sick often meant encephalitis — a swelling of the brain. Epidemiologist led an on-site outbreak investigation back then and is now based at Johns Hopkins University. She says, "The signs and symptoms of encephalitis are fever, headache, but often altered mental status or coma." Disorientation and seizures were common. "But many of these patients also had respiratory disease," Gurley adds, which often led to coughing, vomiting and difficulty breathing.

The virus appeared to be spreading through respiratory droplets and saliva. And the sicker people got, the more infectious they became.

For Khokon and his wife, Anwara, the nightmare continued for weeks as they watched relative after relative get sick, suffer and die. Khokon's older brother, his sister, two uncles, his aunt, his nephew and his mom and dad ... all dead. It was numbing. "In Bangla, they say 'it is a bad wind' or 'an act of God,'" explains Rahman.

Anwara says, "When people started dying out of the virus, people were very afraid. No one came here! Nobody, not even a dog came to this house."

And then, the two of them came down with the virus. (Because the disease carries such a stigma, we are using only their first names.) "I actually have no recollection of that time," says Khokon. "I don't even remember who carried me to the hospital or who carried me to the bed. I was in no shape to remember anything. Me and my wife were unconscious. People couldn't say if we were dead or alive."

, currently a professor of medicine at Stanford University, who was in charge of the outbreak investigation for eight years at the International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b). He says it's terrifying, in part, because the virus is so deadly in people. Also, the outbreaks are tightly clustered. "And so the people who are sick know each other," he says. "And because of this, it is a clear community crisis."

In addition, part of what makes Nipah so worrisome is that its history offers evidence that it might, under the right conditions, launch a pandemic. It had first shown up in Malaysia and Singapore in the late '90s. Around that time, Malaysia had started at an industrial scale — huge numbers of pigs wedged into cramped conditions. When the pigs got Nipah from local fruit bats, the virus spread easily. And then, pig farmers caught it as well.

, an anthropologist with the icddr,b, remembers a call to join the investigation team. "Our colleague called me and asked, 'Rebeca, would you like to go? Are you ready?' I said, 'Yes, I am ready to go there.'"

The next morning, Sultana drove with the team from Dhaka to Thakurgaon. Once she arrived in the village, she went straight to the home of patient zero. "I tried to talk to the elder sister-in-law of the guy who died," she says, "and she was so upset and she just ran and came to me, and hugged me and started crying."

Getting that close to her scared Sultana. As , who leads the Emerging Pathogen research group at icddr,b, says, doing this work is like putting "your soul in your hand. You don't know what is waiting for you in the field."

But Sultana's heart went out to the woman. And she hugged her back. She said to her, "Please don't worry. We're here." She explained that although they didn't know for sure what had caused her relatives to fall ill, "we are here to understand why this happened" by listening openly to the people who had witnessed Nipah firsthand.

(At the research center icddr,b, anthropologists are routinely asked to join these kinds of outbreak investigations when trying to piece together routes of transmission. Their job, in Sultana's words, is "to learn from the community." As Sultana's colleague, , says, "Our role as anthropologists, when we get into the community, first we give them space to listen to them — their anger, their stress. But we didn't respond, 'OK, this is not right, or this is wrong.'")

After Sultana finished her preliminary interviews, she then asked the community to meet her in the town market to help draw a map of the village. About two dozen people showed up. "I don't do anything," she explains. "I just ask questions. And then they draw it."

, a veterinarian and infectious disease specialist at the icddr,b, explains that the consumption of raw date palm sap "is not something you can control. You cannot send police to every house, every village to stop them drinking it. It is not possible."

in which the actors explain how to collect the sap safely — by putting a protective skirt (called a "bana") around the part of the tree with the tap, which keeps the bats out. But people don't always do it. So not every tree is protected. And the spillovers of Nipah virus from bats to people have continued.

Two tricks are the key to Nipah's persistence

It has been 20 years since the harrowing, practically yearly outbreaks started rocking Bangladesh, claiming more than 200 lives to date. And still there's no treatment for Nipah. There's no vaccine. It remains on the with pandemic potential. That's because it has two main tricks.

First, it can jump between species. "We've shown cattle, goats, pigs, cats, dogs can all get infected with Nipah and have been infected with Nipah in Bangladesh," says Gurley. "We don't know how." Perhaps, she says, it's through sap or dropped fruit. Or for pigs and carnivores, it may be through scavenging bat carcasses or placentas. "We're starting a new study to try to figure this out," Gurley says.

The second trick is that Nipah spreads from person to person. So far, Nipah doesn't do a particularly good job of that because the virus tends to kill its host. That means that despite these nearly yearly outbreaks in Bangladesh (with a larger one every four or five years), each has fizzled relatively fast. But each time Nipah makes that leap from bat to person, it gets another chance to find the right combination of mutations to become more transmissible, which could propel it into the realm of a deadly pandemic.

"If we want to contain the virus," says Islam, "we have to understand the virus."

, who heads up the One Health Laboratory at icddr,b, says this is the information they need to ultimately conquer the virus. And yet, "we are at the very earliest stages of preparing ourselves to combat Nipah," he confesses.

Nabbing bats and pondering a glass of date sap

The coming dawn is full of sound. Multiple calls to morning prayer from nearby mosques envelop the small research team. Jackals cackle. And birds flute.

Finally, about an hour before daybreak, a female bat is caught in the net. The team brings her down to earth and untangles her with care. She's big — an adult's wingspan easily reaches 3 feet. Her body is brown and furry. The wings are deep black, like a silky, papery fabric. Islam points out her big eyes, like two orbs of amber staring back.

"If it gets the chance," Islam cautions, "it will bite you, like, 10, 15 times. They're very bite-y." To avoid such an outcome, the team has the bat well restrained. The researcher whose hand is in the most vulnerable position has protected himself with a thick glove.

The team finishes untangling the bat and places her in a cotton bag. For now, the bag hangs from a line strung between two trees. It's possible to just make out the contorting and wriggling bat inside.

The researchers nab one more bat, then call it quits. It's getting too light, and any remaining bats will easily spot and avoid the net. They'll transport the animals to a local one-room lab, but not in a van. "Sometimes bats urinate on themselves to mark them," Islam explains. "So if you carry it in the van, the whole van will be stinking."

So they put the bats into a little three-wheeled car and ferry them to the lab some 20 minutes away, where they'll take blood and urine samples. When they're done, they'll release the two bats.

On the drive to the lab, Islam makes a pit stop at a village with a household that's harvesting date palm sap. "It is possible that they will offer you a glass of sap," he remarks to the group. "Please gently deny it, OK?"

When Islam arrives, he walks up to a huge metal tray over a fire. The air is sugary. Gallons of caramel-colored sap are at a rolling boil. It's thickening into molasses.

"It's really sweet," says Muhammad Seraj Khan, the 74-year-old property owner. "It gets sold all around the village. People will buy it to make household sweets and cakes."

The molasses, says Islam, is harmless — any virus gets cooked away. But that's not the case with raw sap. Still, the villagers like to down glasses of the traditional delicacy when they have the chance. And before Islam leaves, Khan offers some of the raw sap.

And there it is — a slightly cloudy liquid. A delicacy and possible poison all at once, because you never know if that invisible menace is lurking within the sweetness.

New York Times, The British Medical JournalThe Guardian