JUANA SUMMERS, HOST:
Three years ago today, the World Health Organization declared COVID-19 a public health emergency of international concern. That emergency eventually turned into one of the world's deadliest pandemics. To keep this from happening again, scientists have been studying how to detect and stop viruses with pandemic potential.
AILSA CHANG, HOST:
One of those is the deadly Nipah virus. Today, to kick off our series Hidden Viruses: Stopping The Next Pandemic Before It Starts, NPR's Ari Daniel takes us to a part of the world known as the Nipah Belt.
ARI DANIEL, BYLINE: It's early morning in a lush, rural community in central Bangladesh. I'm with a group, and we've just made a pit stop in a village within the district of Faridpur, deep in the heart of the Nipah Belt. It's the start of the season when sap is harvested from date palm trees and is then turned into molasses. That's what I'm here to see.
(SOUNDBITE OF FIRE CRACKLING)
DANIEL: I walk up to a huge metal tray over a fire. Gallons of caramel-colored sap are at a rolling boil, thickening into molasses. Mohammed Siraj Khan (ph) is the 74-year-old property owner.
MOHAMMED SIRAJ KHAN: (Through interpreter) This is actually a delicacy in Bangladesh. Mostly, we make cakes and sweets with it.
DANIEL: Then I'm offered some of the raw sap to drink. And there it is, the slightly cloudy liquid I've heard so much about, a delicacy and possible poison all at once. I was warned that this exact thing might happen. I was given advice about what to say.
(SOUNDBITE OF CHICKEN CLUCKING)
DANIEL: The evening before, just a few miles away, I pay a visit to a local family. A 50-year-old man named Kokon (ph) sits outside his home beside a rice paddy. A fiery beard dyed a bright orange rings his chin. And he says he'll never forget the spring of 2004, when the procession of disease and death came on suddenly.
KOKON: (Through interpreter) The first one was the mother-in-law of my elder brother. She was really sick. She had been sick for some time. Then she died. We took her to the grave. Then my father got sick.
DANIEL: Kokon stares off into the distance as he tells me his father was a spiritual leader in the community. When he became ill, many came to pay their respects.
KOKON: (Through interpreter) Just 12 days after my father died, suddenly, he was no more.
DANIEL: As for the visitors, they also got sick. One traveled to an adjacent village, where four more people fell ill.
MAHMUDUR RAHMAN: It was not understood what was happening.
DANIEL: Mahmudur Rahman is the former director of the Institute of Epidemiology, Disease Control and Research for the Bangladeshi government.
RAHMAN: Some people who were transporting the patients to the hospital were also getting sick.
DANIEL: Sick often meant encephalitis, a swelling of the brain. Epidemiologist Emily Gurley, now at Johns Hopkins University, was leading an on-site investigation at the time.
EMILY GURLEY: The signs and symptoms of encephalitis are, well, fever, headache but often altered mental status or coma, seizures.
DANIEL: Then Kokon and his wife Anwara (ph) fell ill. It's why I'm only using their first names - because the disease carries stigma.
ANWARA: (Through interpreter) People couldn't say if we are dead or alive. They said that we had high fever. Like, whenever they were touching us, it was like touching fire.
DANIEL: Miraculously, they both survived. But Kokon's older brother, his sister, two uncles, his aunt, his nephew and his mom and dad - all dead. This outbreak, says Dr. Rahman, made something brutally evident.
RAHMAN: This is obviously showing that we are unable to control it, and it is spreading.
DANIEL: And with roughly 70% of those who got it dying, what virus could be that lethal?
GURLEY: We didn't know. I was just looking at the data. I was just looking at data to see what do we think is going on here?
DANIEL: A few weeks later, Gurley and her colleagues got an email from the CDC in Atlanta that this was the Nipah virus. They knew the virus came from bats 'cause in the '90s in Malaysia, when it first emerged, Nipah was spreading from local fruit bats to pigs to pig farmers. That's bad enough, but in Bangladesh, the virus was behaving differently.
GURLEY: It was being transmitted person to person, which had never been reported before. So that was a scary time.
DANIEL: An urgent question hung over Gurley. Just how did Nipah spill over from bats into humans in the first place? That was what needed answering to shut this thing down.
GURLEY: So what we did is walk through the village and thought about all the possible ways people could come into contact with bats or bat secretions, bat urine, bat saliva.
DANIEL: Finding this link - it's agonizingly slow work that takes years because an outbreak blazes quickly. The victims are dead, and eyewitnesses often flee or clam up. But the outbreaks kept happening almost every year afterwards, which was deeply worrying to experts because each time the virus leaps from bat to person, it gets another opportunity to mutate, possibly becoming more transmissible - the fear being the right combination of mutations could propel it into the realm of a deadly pandemic. Finally, the connection emerged, one that offered a remedy for stopping the Nipah spillovers. But the researchers needed more evidence. In 2007, they got their chance.
REBECA SULTANA: Our colleague called me and asked, Rebeca, are you ready? I said, yes, I'm ready to go there.
DANIEL: The next morning, anthropologist Rebeca Sultana joined the Nipah outbreak investigation team. She's with the International Centre for Diarrheal Disease Research, Bangladesh, or icddr,b for short. When she arrived in the village, she went straight to the home of patient zero.
SULTANA: I tried to talk to the elder sister-in-law of the guy who died. And she was so upset, and she just ran and came to me and hugged me and started crying.
DANIEL: Getting that close to her scared Sultana. As one Nipah researcher told me, doing this work is like putting your soul in your hand. But Sultana - she hugged her back and said...
SULTANA: Please don't worry. We are here to understand why this happened.
DANIEL: She asked the community to meet her in the town market to help her draw a map of the village. About two dozen people showed up.
SULTANA: I don't do anything. I just ask question, and then they draw it.
DANIEL: Using sticks in the dirt, the residents roughed out houses, roads, bat roosts, and then they began sketching in date palm trees.
SULTANA: This is the first time the people informed me, you know, there is a date palm tree, and there is a sap harvester in this community.
DANIEL: Sultana hadn't seen the date palm trees on the drive in. But staring back at her from the dirt, there it was, the possible link between how the fruit bats had passed Nipah into this community - through the drinking of the sweet sap. Emily Gurley.
GURLEY: We thought, well, this would be a great way to have contact with bat secretions because I'm sure the bats love the sap and so do people.
DANIEL: So Rebeca Sultana and her colleagues tracked down that sap harvester, and he led them to a few pals of the guy who was patient zero.
SULTANA: They said, we all used to drink raw sap in the morning.
DANIEL: This was Sultana's aha moment, that patient zero had had raw sap before falling ill. The line between the bats, the sap and the outbreaks was becoming clear. Over the next few years, researchers took infrared cameras and caught the bats at night drinking from and sometimes peeing into the same stream of sap that people were harvesting. Eventually, the government had enough evidence to launch a campaign against the drinking of raw sap. But many people have continued to drink the sap, and the spillovers of Nipah virus from bats to people have continued, too.
(SOUNDBITE OF PLANTS RUSTLING)
DANIEL: It's December 1, the beginning of what's known around here notoriously has Nipah season, the four months when the virus is most likely to show up. This is when the sap is harvested and when Zhahirul Islam keeps an especially close eye on Nipah.
ZHAHIRUL ISLAM: If we want to contain the virus, we have to understand the virus.
DANIEL: It's 3 in the morning. Islam stops at the edge of a patch of forest and looks up into the sky. A net stretches between two mahogany trees.
Why are we out here so early?
ISLAM: Because the bats soon start coming back from foraging after 3. So this is the best time to catch them.
DANIEL: Islam is a veterinarian and infectious disease specialist at the icddr,b. He's searching for another way to stop Nipah. Every month, he brings a team out here near Faridpur to capture bats. The answer isn't getting rid of these animals. Islam has great respect for their importance to the local ecosystem. Rather, years of studying thousands of greater Indian fruit bats have shown that most of them do carry Nipah virus. But here's the thing - fewer than 1% of them actually release it into the environment through their urine or saliva. Why do so few of these animals shed the virus? Islam thinks for that small group, it's likely connected to stress.
ISLAM: Is it lack of food? Is it pregnancy stress? Is it lack of habitat?
DANIEL: Knowing what's behind the shedding could help Islam and his colleagues figure out how to keep Nipah from infecting people in the first place.
(SOUNDBITE OF BATS CHIRPING)
DANIEL: The coming dawn is full of sound. There are jackals and fruit bats.
What just happened?
UNIDENTIFIED PERSON: We able to capture bat.
DANIEL: OK. So a bat just flew into the net. The bat's body is like a brown and furry, and the wings are just deep black, like a silky papery fabric.
ISLAM: If you go around, you'll see the big eyes.
DANIEL: I gaze into them, like two orbs of amber. She's big. An adult's wingspan easily reaches 3 feet.
ISLAM: If it gets the chance, it'll bite you, like, 10, 15 times. They're very bitey.
DANIEL: Just untangled it.
The team nabs one more bat and then calls it quits. It's getting too light. They put the bats into a three-wheeler and ferry them to a local lab, an unassuming one-room building, and yet a crucial outpost in the battle against Nipah. It's where the researchers will sample blood and urine from the bats. And once they're done, they'll release the animals back into the woods. It's on the drive to the lab when Islam makes a pit stop in that village. He wants to show me the date palm trees, the boiling molasses. That's when he'd given me that advice.
ISLAM: It is possible that they will offer you a glass of sap. Please, gently deny it, OK?
DANIEL: The bubbling molasses I see before me is harmless. Any virus gets cooked away. And to be fair, Khan, the property owner, he doesn't recommend drinking it raw. But before we leave, sure enough, I'm offered a taste of the cool, cloudy sap, a chalice of what could be delectable poison. I smell the sweet air, and I politely decline. Ari Daniel, NPR News. Transcript provided by NPR, Copyright NPR.