Shortly after dawn on a cool morning in late August, a three-member team from the Centers for Disease Control and Prevention in Atlanta, Georgia, along with two colleagues, set out in a four-wheel-drive Toyota from a hotel in central Uganda. After a 15-minute drive, they parked on a dirt road in front of an abandoned brick house. Mist shrouded the lush, hilly landscape, and fields glistened with dew. “We checked this place yesterday,” said Megan Vodzak, a Bucknell University graduate student in biology who had been invited to join the CDC mission. “We were walking around and they flew out, and we’re hoping they will have moved back in.” A cluster of schoolchildren watched, rapt, from a banana grove across the road. The team put on blue surgical gowns, caps, black leather gloves and rubber boots. They covered their faces with respirators and plastic face shields. “Protection against bat poop,” Vodzak told me. Jonathan Towner, the team leader, a lanky 46-year-old with tousled black hair and a no-nonsense manner, peeked through a cobweb-draped door frame into the dark interior. Then they got to work.
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Towner—as well as Luke Nyakarahuka, an epidemiologist from the Ugandan Ministry of Health, and Brian Bird and Brian Amman, scientists with the CDC—unrolled a “mist net,” a large hairnet-like apparatus fastened to two eight-foot-tall metal poles. They stretched it across the doorway, sealing off the entrance. Towner moved to the rear of the house. Then, with a cry of “Here we go,” he hurled rocks onto the corrugated-tin roof and against metal shutters, sending a dozen panicked bats, some of them possibly infected with Ebola, toward the doorway and into the trap.
The team had arrived here from Atlanta on August 8, eleven days after confirmation of an outbreak of the Ebola virus. They brought with them 13 trunks with biohazard suits, surgical gowns, toe tags, nets, respirators and other equipment. Their mission: to discover exactly how Ebola is transmitted to human beings.
Towner had chosen as his team’s base the Hotel Starlight in Karaguuza, in Kibaale district, a fertile and undeveloped pocket of Uganda, 120 miles west of the capital, Kampala. That’s where I met them, two weeks after their arrival. For the past 13 days, they had been trapping hundreds of common Ethiopian epauletted fruit bats (Epomophorus labiatus) in caves, trees and abandoned houses, and were reaching the end of their fieldwork. Towner suspected that the creatures harbored Ebola, and he was gathering as many specimens as he could. Based on his studies of Egyptian fruit bats, which carry another lethal pathogen, known as Marburg virus, Towner calculated that between 2 and 5 percent of the epauletted fruit bats were likely to be virus carriers. “We need to catch a fair number,” he told me, “to be able to find those few bats that are actively infected.”
Ebola was first identified in Zaire (now Congo) in 1976, near the Congo River tributary that gave the virus its name. It has been terrifying and mystifying the world ever since. Ebola is incurable, of unknown origin and highly infectious, and the symptoms are not pretty. When Ebola invades a human being, it incubates for a period of seven to ten days on average, then explodes with catastrophic force. Infected cells begin producing massive amounts of cytokine, tiny protein molecules that are extensively used in intercellular communication. This overproduction of cytokine wreaks havoc on the immune system and disrupts the normal behavior of the liver, kidneys, respiratory system, skin and blood. In extreme cases, small clots form everywhere, a process known as disseminated intravascular coagulation, followed by hemorrhaging. Blood fills the intestines, the digestive tract and the bladder, spilling out of the nose, eyes and mouth. Death occurs within a week. The virus spreads through infected blood and other bodily fluids; the corpse of an Ebola victim remains “hot” for days, and direct contact with a dead body is one of the main paths of transmission.
In 1976, in a remote corner of Zaire, 318 people were infected by Ebola and 280 died before health officials managed to contain it. Nineteen years later, in Kikwit, Zaire, 254 people out of 315 infected perished of the same highly lethal strain. Four outbreaks have occurred in Uganda during the past 12 years. The worst appeared in the northern town of Gulu in the fall of 2000. More than 400 inhabitants were infected and 224 died from a strain of the virus called Ebola Sudan, which kills about 50 percent of those it infects. Seven years later, a new strain, Ebola Bundibugyo, killed 42 Ugandans in the district of that name.
A person stricken with Ebola wages a lonely, often agonizing battle for survival. “It becomes an arms race,” says the investigating team’s Brian Bird, veterinary medical officer and an expert in pathogens at the CDC. “The virus wants to make new copies of itself, and the human body wants to stop it from doing so. Most of the time, the virus wins.” The most lethal strain, Ebola Zaire, attacks every organ, including the skin, and kills between eight and nine of every ten people it infects. The virus strain, the amount of pathogen that enters the body, the resilience of the immune system—and pure luck—all determine whether a patient will live or die.
The virus arrived this time, as it usually does, by stealth. In mid-June 2012, a young woman named Winnie Mbabazi staggered into a health clinic in Nyanswiga, a farming village in Kibaale district. She complained of chills, a severe headache and a high fever. Nurses gave her antimalarial tablets and sent her home to rest. But her symptoms worsened, and two days later she returned to the clinic. Mbabazi died there overnight on June 21.
Two days after Mbabazi’s death, a dozen family members from a three-house compound in Nyanswiga attended her funeral. Many wept and caressed the corpse, following Ugandan custom, before it was lowered into the ground. Soon, most of them began to fall ill too. “Everybody was saying, ‘I have a fever,’” said one surviving family member. Five people from the compound died between July 1 and July 5, and four more during the next two weeks. One victim died at home, two expired at a local health clinic, two brothers died at the home of a local faith healer, and four died at the government hospital, in the nearby market town of Kagadi. The survivors “could not imagine what was killing their family members,” said Jose Tusuubira, a nurse at the facility. “They said, ‘It is witchcraft.’”
Health workers at Kagadi Hospital didn’t suspect anything unusual. “Malaria is the first thing you think of in Africa when people get sick,” says Jackson Amone, an epidemiologist and physician at the Ugandan health ministry in Kampala. “If you’re not responding to treatment, the [health workers] might be thinking that the problem is counterfeit medicine.” Then, on July 20, one of their own succumbed to high fever: Claire Muhumuza, 42, a nurse at Kagadi Hospital who had tended several members of the doomed family. Only then did the health ministry decide to take a closer look.