0812 GMT March 26, 2019
Come night, the tiny fruit bats whoosh out, tens of thousands of them at a time, filling the air with their high-pitched chirping before disappearing into the black sky, ndtv.com reported.
The bats carry the deadly Marburg virus, as fearsome and mysterious as its cousin Ebola.
Scientists know that the virus starts in these animals, and they know that when it spreads to humans it is lethal – Marburg kills up to nine in 10 of its victims, sometimes within a week.
But they do not know much about what happens in between.
That is where the bats come in. No one is sure where they go each night. So a team of scientists from the US Centers for Disease Control and Prevention traveled to Uganda to track their movements in the hopes that spying on their nightly escapades could help prevent the spread of one of the world's most dreaded diseases.
Because there is a close relationship between Marburg and Ebola, the scientists were also hopeful that progress on one virus could help solve the puzzle of the other.
Their task was to glue tiny GPS trackers on the backs of 20 bats so they could follow their movements.
"We want to know where they're going on a nightly basis," said Jonathan Towner, 52, who heads a CDC team that specializes in how these deadly viruses are spread.
If the animals were feeding on particular fruit trees, that information could identify communities most at risk and help prevent future outbreaks.
"It's much easier to put together a picture and say to local authorities, 'Look, this could be potentially how the virus is spread, this is what the bats are doing’."
US officials are so concerned about Marburg becoming a global threat that the CDC is asking the Pentagon's Defense Threat Reduction Agency to pay for the bat trackers, which each cost about $1,000. The CDC is hoping to track more of these Rousettus aegyptiacus bats in several other caves in Uganda.
Marburg's potential to spread was made clear a decade ago when a pair of tourists on separate trips walked into the cave looking for adventure and walked out with the virus. A Dutch woman died 13 days after her visit. The other visitor, an American woman named Michelle Barnes, survived after a long, painful illness. The cave was closed to tourists in 2008.
Marburg was first identified in 1967 when a shipment of infected African green monkeys from Uganda was sent to laboratories in Marburg and Frankfurt, Germany, and Belgrade, in then-Yugoslavia. Seven lab workers died within about a week. Since then, a dozen outbreaks have been reported, killing hundreds of people. Most took place near bat-infested caves or mines, including one last fall along Uganda's eastern border with Kenya. Of four family members sickened, only one survived.
For the CDC scientists, success hinged on getting the tracking units, which are half the size of a pen cap, to stay on a bat body that is only about six inches long. A practice run in Atlanta with the same device on the same kind of bat in a special CDC laboratory had failed. Trackers had slipped off or had been chewed by the bats.
"I have no idea how well this is going to go because it's the first time we've tried it," Towner said.
"It could end up in total flames."
Well before you see the bats – about 50,000 live in the cave – you hear their squeaks and chatter and smell the ammonia from their guano, which also covers the cave's rocky floor. One false step could lead to a fall into a stream underneath. Another could land the scientists on one of the African rock pythons or forest cobras that slither along the ground.
Towner and CDC colleague Brian Amman, 54, discovered a decade ago that this Egyptian fruit bat is a natural reservoir for Marburg. That means the virus can live and grow inside the bats without harming the animal, and be excreted in its urine, feces or saliva.
By comparison, more than 40 years and over two dozen outbreaks after Ebola emerged in Central Africa, researchers still do not know what animal or animals carry it, much less how it spreads to people.
The bat team included CDC scientist Jennifer McQuiston and Luke Nyakarahuka, an epidemiologist at the Uganda Virus Research Institute, a longtime CDC partner. The CDC allowed a Washington Post reporter and photographer to accompany the team.
In a clearing of the Maramagambo Forest, the scientists' workstation was a table under a tent. Curious baboons perched on nearby tree stumps. Black-and-white colobus monkeys peered from overhead branches. On a drive through the park in search of other bat roosts, the scientists' Toyota Land Cruiser yielded the right of way to a majestic waterbuck, its long, curved horns glinting in the sun.
Their task was to catch and glue trackers on 10 bats the first day, repeat the next day.
The tracking software has already prompted a stream of curses from Amman. To test it again, McQuiston and Nyakarahuka each cupped a tiny unit in their palms and jogged around the clearing to simulate bats on the move. That was supposed to trigger readings. But the screen on Amman's clunky CDC-issued laptop remained blank.
"If it comes back and says zero I don't know what we're going to do," Amman muttered. Several minutes passed in silence. Then, ever so slowly, data points started to show up.
Now they could head to the cave.
Towner and Amman suited up in special helmets and face shields connected to battery-powered respirators that muffled their voices. Underneath protective gowns they wore Kevlar-lined waist-high pants to guard against snake bites. On their hands were cut-resistant leather gloves, like those worn by law enforcement, over two pairs of medical gloves to protect against bat bites. Towner also had a video mounted on his helmet.
The bats take flight, which is when they relieve themselves of what Amman calls the "rain of pee and poo."
Amman, holding a net, heads to where Towner was pointing, veering far away from an enormous python. He returned with two bats, which went into a pillowcase Towner was holding. Each pillowcase would hold about five bats since bats do not like to be alone.
Only males were caught; the scientists did not want to burden females carrying pups.
Amman dreaded the prospect of using sutures because they are messy and complicated. But given the failure in Atlanta, he had brought the necessary kit. He hoped a last-minute purchase of different veterinary glue may do the trick.
Towner lifted the first bat out of a pillowcase, cradling it in his gloved hands. The bat was calm. Its big brown eyes blinked, unaccustomed to the light. Towner placed it stomach down, wings tucked in. One hand covered its head, the other its feet.
He squeezed a thin line of glue on its back, another line of glue on the tracker and pressed down gently but firmly.
"WOO-HOO!" Amman shouted, relief washing over his face. Up went his arms, signaling a touchdown.
"I'm so happy, Jon. I didn't want to suture them. . . . I gotta tell ya. This is just better than Christmas," he gushed.
They glued the remaining units and released the bats.
Towner uncupped his hands to free the last bat.
Then, the scientists waited, unsure whether the batteries would last, whether the signal would be able to break through cloud cover to reach the satellite, whether technology would be able to capture this crucial flight of nature.
For now, the most effective way to battle outbreaks like Marburg is stopping them at their source.
The bat cave in Queen Elizabeth National Park in Uganda had always been a popular tourist attraction.
"We used to have tourists walk down there," said park veterinarian Margaret Driciru.
"Health-wise, it really was not the right idea."
Most likely, although a few cases which have been reported due to visiting the cave, a large number of Marburg cases have gone undetected because the disease symptoms are similar to malaria and typhoid fever, common illnesses across much of Africa.
Now the park has posted warning signs that bats can carry the Marburg virus. Visitors must stay in an enclosed observatory with glass windows about 65 yards away.
The Uganda Wildlife Authority, which runs the country's parks and is helping the CDC, also has an enormous stake in the project's success. Wildlife is the top tourist attraction, and tourism is Uganda's biggest source of revenue. But if wildlife carry diseases that kill humans and nonhuman primates, like the park's famed chimps, tourists will stop coming.
In a meeting with a park warden, Towner and Amman explained how the trackers may show bats traveling to nearby towns in search of fruit. Any fruit the bat bites can be smeared with Marburg; a person, monkey or other animal eating that fruit can get infected.
After outbreaks of Nipah virus killed scores of people in Bangladesh over the past decade or so, scientists discovered that humans were getting infected from drinking virus-infected date palm sap. The sap is collected overnight from the trees. Bats were flying to the containers to drink the sweet sap draining from trees into collection pots. In the process, they were contaminating it with their saliva and excretions that are known to contain the virus.
Photographic evidence of bats urinating in the containers helped persuade villagers about Nipah's dangers. Scientists hope flight patterns of the Marburg-carrying bats could be similarly persuasive.
During last fall's Marburg outbreak that sickened a cattle farmer's family, "a traditional healer told the family (the sickness) was because of family conflicts," Nyakarahuka said.
Ugandan officials eventually met with nearly 150 community religious leaders and elders as part of outreach and education about the disease.
At the Kitaka gold mine, about 30 miles northeast of the bat cave, some residents also doubt that bats can cause serious disease despite a Marburg outbreak in 2007 that infected four miners, killing one.
It was the CDC team's last day in the forest. Time for the final test.
Bat No. 14 had logged more than 3,000 data points in one night. That meant he flew a good distance. So did Bat No. 11.
Days later, Amman would be able to tell that the bats flew in different directions, some traveling up to 15 miles. At least two had flown southwest toward a spot near another town on the other side of the forest. That could mean a broader area of infection risk.
Perhaps the bats had headed to a big fruit tree. Or another cave. Travel between far-flung roosts could be one way the virus is transmitted to other colonies. GPS coordinates showed the two bats had flown to an area two miles due east from an existing road. That was definitely something to be investigated, perhaps on a future trip.
For now though, the pair of scientists were quietly thrilled that their effort, years in the making, had worked.