The scientists are from the Centers for Disease Control and Prevention, and they have embarked on this watery journey to solve a decades-old mystery about a rare and fatal disease: monkeypox.
A cousin to the deadly smallpox virus, the monkeypox virus initially infects people through contact with wild animals and can then spread from person to person. The disease produces fever and a rash that often turns into painful lesions that can feel like cigarette burns. It kills up to 1 in 10 of its victims, similar to pneumonic plague, and is particularly dangerous in children. Monkeypox is on the U.S. government list of pathogens such as anthrax and Ebola with the greatest potential to threaten human health. There is no cure.
Over the past year, reports of monkeypox have flared alarmingly across Africa, one of several animal-borne diseases that have raised anxiety around the globe. The Congolese government invited CDC researchers here to track the disease and train local scientists. Understanding the virus and how it spreads during an outbreak is key to stopping it and protecting people from the deadly disease.
In Congo Republic, many suspected monkeypox cases trace back to the village of Manfouete, a six-hour boat trip from the nearest airport. The village has 1,600 people, no electricity and no running water. The scientists are traveling upriver in a big motorized boat that looks like an open-air school bus. They must bring everything they need for their work. So a second boat - a long, wooden dugout canoe - will follow later carrying most of their supplies: boxes of traps and test tubes, a portable centrifuge, jerrycans of gasoline, a 25-kilogram sack of rice and lots of bottled water.
On the river, the scientists in their noisy boat pass men and women gracefully paddling their own wooden dugout canoes and standing with their feet far apart for balance. Some ferry entire families; others carry baskets of vegetables, smoked fish or firewood. The scientists pass huts with dried mud walls and palm-thatched roofs where brightly colored clothes are laid out to dry.
"Mbote! Mbote!" - Hello! - children shout from the riverbanks. Biologists Jeff Doty and Yoshinori Nakazawa, part of the CDC team, wave back.
The boat follows the Ubangi River to the twisting Motaba River, where the water is smooth and still and stained the color of black tea.
The last few miles are difficult to navigate. As the sun dips low in the western sky, everyone worries about arriving after dark, when chances are highest for run-ins with hippos, considered the most dangerous animals in Africa.
The sun is setting when the jungle falls away to reveal a sudden clearing framed by tall grass: Manfouete. The only structure visible from the river is the village school, where the scientists will sleep during their stay.
Working with a dozen Congolese and international experts who are part of the team, they move wooden desks and benches out of two classrooms and pitch tents to protect themselves from biting insects during the night. (They avoid a third classroom, where a two-foot-high termite mound has sprouted from the concrete floor.)
When that work is done, there is still no sign of the dugout canoe carrying the food. So the scientists go to bed hungry, listening to the rhythmic thrum and shrill noises of the jungle.
Manfouete lies in the tropical rain forest of central Africa, just north of the equator. Leprosy and other infectious diseases long wiped out elsewhere still lurk in this remote corner of the world. Ebola, caused by one of the most dangerous pathogens ever discovered, is considered endemic in neighboring Congo, where eight outbreaks have been recorded in the past 40 years.
The United States experienced a monkeypox outbreak in 2003. An exotic pet dealer imported 800 animals from Africa, including giant pouched rats, dormice and rope squirrels. While the animals were housed in a facility in Illinois, some of them infected prairie dogs that were later sold as pets. Forty-seven people in six Midwestern states were sickened, all of whom recovered. The youngest was a 3-year-old girl bitten on the finger by her new pet prairie dog.
Worldwide, animal-borne infectious diseases that jump to humans are on the rise. Tropical rain forests, with their rich diversity of animal life, are disease hot spots. An outbreak that begins in a remote village such as Manfouete can reach major cities on any continent in less than 36 hours, blossoming into a global crisis.
In the Congo Republic, the monkeypox outbreak began in January with a hunter from Manfouete. Since then, at least 88 suspected cases of monkeypox have been reported throughout the country, and six people have died, including one confirmed case from Manfouete.
Some people were infected while caring for sick relatives. Others became sick through contact with wild animals or while hunting or preparing this critical source of protein in the local diet. But scientists don't know which animals carry the virus.
Despite its name, monkeypox is probably not spread by monkeys. It was discovered in research monkeys in Denmark in 1958. Giant pouched rats, dormice and squirrels are the chief suspects, but there could be others. If the sources could be identified, villagers could avoid those species and prevent future outbreaks.
So in August, the CDC dispatched an ecological investigation team from Atlanta to try to find the sources. In addition to Doty and Nakazawa, the mission includes a third biologist, Clint Morgan, and Jennifer McQuiston, deputy director of the CDC's Division of High-Consequence Pathogens.
The biologists are the core team. Doty, 39, is outgoing, with a wry sense of humor. He has learned enough Lingala, a local language, to converse easily with villagers. Nakazawa, 38, is the boss on the mission. More reserved, he speaks five languages, including French, Congo Republic's official language. Morgan, 26, is the team's junior member, making his first trip to Africa.
The CDC gave a rare opportunity to a Washington Post reporter and photographer to accompany them.
From Atlanta, the team flew to Brazzaville, the capital of Congo Republic, with 15 boxes of supplies, including a 48-ounce jar of Jif creamy peanut butter for use in making bait. In nearby Kinshasa, they picked up a tank of liquid nitrogen to preserve animal samples at minus-346 degrees Fahrenheit on the long trip back to Atlanta for analysis.
In Brazzaville, the scientists are joined by Congolese and international experts who help with translation and logistics. From there, the group flew 450 miles north to Impfondo.
In Impfondo, they completed their shopping at the town's sprawling market under a relentless equatorial sun. Doty checked items off a handwritten shopping list: Generator. Power strips. Hammer and nails. Shovels and machetes. Rubber boots. Plastic buckets. Canned corned beef and dried beans. Soap. Toilet paper.
Then they loaded the boats and set off.
On the first full day in Manfouete, everyone on the team is up before dawn. There's still no sign of the wooden dugout.
Doty, normally unflappable, scans the river anxiously. Maybe the motor broke down, he says. Or the boat drivers were robbed. There's no way to communicate with them.
Logistics are difficult for field research like this. On a previous mission in neighboring Congo, Doty says, a planeload of supplies didn't arrive until the second-to-last day. On another investigation in Congo, the team's only truck hit a motorcycle and plunged into a river.
After two hours, the dugout appears, and the work begins in earnest. Supplies are unloaded, bucket-brigade style. Men from the village are hired to build a makeshift laboratory by cutting bamboo from the forest with machetes and wrapping tarp around the fresh-cut poles. The village secretary's wife is hired to cook one daily meal: rice and beans, fish stew and roast goat. Hunters are hired to lead the way into the forest to set the traps.
Detailed negotiations over payment follow in a mix of English, French and Lingala. The village secretary records the agreements, longhand, in a large black ledger. Every evening, Doty or Nakazawa will pay the villagers in local currency.
The scientists then set about preparing the traps. They will be baited each afternoon and checked the next day at dawn. In some, the bait is peanut butter mixed with oats and seeds. In others, it is diced coconut cooked in oil and coated with peanut butter.
The rich smell of peanut butter makes the Americans hungry; none of them has eaten a full meal in more than a day. McQuiston sneaks a gloved fingerful.
Led by the hunters, the scientists carry the traps into the dark thicket of vines and trees surrounding the village. There are metal rectangular boxes and wire cages that snap shut when an animal walks inside. The most low-tech are pitfall traps: plastic buckets set in holes in the ground and covered with tarps, best for catching small rodents.
The smell of earth is heavy and moist as McQuiston and Doty kneel on the jungle floor digging holes for the buckets. Their hands are black with dirt.
"This is very labor-intensive," McQuiston says.
"Yeah, this is not my favorite kind of trap," Doty agrees.
The hunters want to place the wire cages near large dirt mounds at the base of some trees - potential dens of giant pouched rats. Known as "motomba," the animals are a leading suspect as a monkeypox host.
To figure out how the disease spreads, the scientists want to know whether jungle animals live on the ground or in the trees and whether they emerge during the day or at night.
"It's the ecology of how the virus is being circulated and transmitted, because you find out what the animals are doing and how they're doing it," Doty says. "Ecology is more complicated than rocket science."
The next day, everyone is eager to check the traps. The team hikes at sunrise into the jungle and splits into groups.
Wearing a headlamp, Doty peers into buckets now full of rainwater from overnight thunderstorms. In the first is a frog, which he scoops out and sets free. (The virus infects mammals, not amphibians.)
Bucket two is empty. So is bucket three.
But the fourth bucket contains a prize: a tiny, dark-gray shrew, partly covered by leaves and twigs. With a gloved hand, Doty grabs it and drops it into a small cloth bag.
Some of the metal traps are also empty; others are full of ants. But then Doty comes to a box next to a fallen log under a canopy of leaves. He keeps it at arm's length as he lifts it and gently presses the trap door. "Esimbi!" he calls out in Lingala. Success!
"One," he says.
After about two hours, the scientists regroup and compare notes. The day's catch: 13 rodents, mostly shrews. No giant pouched rats, but the majority of traps have yet to be set.
"It's a good start," Doty tells Nakazawa.
"Not bad," Nakazawa replies, his ponytail bobbing in agreement.
Angelie Dzabatou-Babeaux, a Congolese health ministry official from Brazzaville who is coordinating efforts on the ground, asks how many animals the scientists hope to catch during their stay.
"We'd like to get 250," Doty replies. "But if we get less, we're still happy."
The teams head back to camp, eager to get a closer look at the animals in their makeshift lab. But word has spread in the village, which has no trained health workers, that foreign scientists are here working on the mysterious disease.
A villager shows up seeking help for his two sick sons. The young men, 17 and 19, have lesions on their bodies. One also has a fever and swollen lymph nodes - signs of a pox infection.
Two weeks earlier, the villager says, their 75-year-old grandfather died. He also had a fever and lesions.
Doty and Nakazawa are not medical doctors. Team members from the World Health Organization and the Office of the United Nations High Commissioner for Refugees step in.
Using sterilized needles, they scrape tissue from the teens' lesions. The 17-year-old says nothing, but his lower lip trembles.
The tissue samples will be analyzed in Brazzaville. Until the results come back, the brothers will be treated as suspected cases of monkeypox. They are given fever-reducing medicine and antibiotics to prevent secondary infections.
Before the CDC team leaves Manfouete, a third brother will come forward with similar symptoms.
Sitting before her hut on a low stool made of forest vine, the mother of the sick boys, Delphine Boutene, explains how she cared for her dying father. At 43, she has 10 children and the saddest eyes in the world.
"I'm afraid that maybe my children also can die," she says softly.
Back at the lab, the biologists examine their catch. All three have received the smallpox vaccine, which is 85 percent effective against monkeypox. To further guard against infection, they wear long blue gowns, two pairs of gloves and battery-powered respirators that cover the entire face and neck. After a few hours, their shirts are soaked through with sweat; the insides of their gloves are also wet.
For each animal, the procedure is the same: The trap number is recorded. The trap's GPS coordinates, captured separately, will permit scientists to pinpoint the homes of animals that test positive.
The animal is anesthetized and its blood drawn with a tiny syringe. Its sex, species and approximate age are recorded, along with its body measurements in millimeters and grams and its reproductive condition.
The scientists also note any sign of wounds or lesions before placing the samples into test tubes. These are then bagged in black, knee-high nylon stockings and dropped into the liquid nitrogen tank.
Creedence Clearwater Revival is playing on Doty's iPhone as he examines one of the rodents.
Nakazawa jots the trap number in a logbook. After a while, their work sounds like a game of bingo.
"Adult, scrotal male," Doty says. "Length, 209; tail, 84; foot, 18; ear, 19; weight, 44."
He notices the animal has bigger ears and footpads than some others.
"Is it a rat?" Nakazawa asks through his respirator.
"Not sure what it is," Doty replies, peering closely at the animal. Its tail looks as though it was cut short, maybe from disease.
"Have you seen any lesion-like things yet?" Morgan asks.
No, Doty says. Not yet.
Lesions could be a sign of infection. An animal in the wild with an active infection could yield live monkeypox virus or DNA evidence of the virus. In the past four decades, scientists have been able to gather live monkeypox virus only twice from wild animals.
Two days before they leave Manfouete, the scientists get what could be a huge break. They catch two giant pouched rats, each nearly three feet long and weighing about three pounds.
The tail of each animal is covered with circular crusted lesions.
They swab the lesions and take samples.
"We had never seen anything just like this before," Doty explains later. It's possible the lesions are from wounds in a fight or from a parasite. The scientists won't know for sure until the samples are tested back in Atlanta.
"It would be great if it's monkeypox," Nakazawa says.
Over 10 days, the CDC team takes samples from 105 animals, including 28 African wood mice, 22 shrews, nine giant pouched rats, two bats and one African brush-tailed porcupine.
It will take several weeks for the liquid nitrogen tank to be cleared into Atlanta, where samples from the lesions on the giant pouched rats will be tested first. If biologists find evidence of monkeypox, they will attempt to grow the virus in the lab, sequence its genes and develop a more complete picture of which virus strains from which animals are infecting people. The entire process could take several months.
For now, the team focuses on leaving Manfouete. Their lab is dismantled and many supplies distributed to the villagers. The generator, traps, personal protective gear and test tubes will be carried back down the river and left in Impfondo for use in future disease outbreaks.
On their last day in the village, the scientists host a farewell dinner under an enormous mango tree as tall as a five-story building. Nearly 150 villagers come, bringing their own bowls and banana leaves to hold the meal of rice and beans, dried fish, goat and saka-saka, a vegetable dish made from cassava leaves.
As sunset approaches, people dance to the pulsating beat of Congolese music. Children get gifts of candy and glow-stick bracelets the scientists have brought from Atlanta.
The next morning is overcast. The clouds turn the river gray, making the green of the trees seem brighter. Villagers turn out to send the scientists off, waving and calling out goodbyes. The scientists wave back.
"Merci," the scientists shout as the boats pull away. "A la prochaine! Until next time!"
And then they're gone, bearing the liquid nitrogen tank and the hope that, somewhere inside it, lies an answer.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)