for which bats serve as reservoirs. So to clarify: That inclusion is tentative. It’s a hypothesis awaiting assessment against further evidence. No one, as of this writing, has isolated any live ebolavirus from a bat—and virus isolation is still the gold standard for identifying a reservoir. That may happen soon; people are trying. Meanwhile the Ebola-in-bats hypothesis seems stronger since Jonathan Towner’s team achieved their isolations of Marburg virus, so closely related, also from bats. And it has been strengthened further, at least a little, by another bit of data added to the ebolavirus dossier about the same time. This bit came in the form of a story about a little girl.
Eric Leroy, the Paris-trained virologist based in Franceville, Gabon, who had been chasing Ebola for more than a decade, led the team that reconstructed the girl’s story. Their new evidence derived not from molecular virology but from old-fashioned epidemiological detective work—interviewing survivors, tracing contacts, discerning patterns. The context was an outbreak of Ebola virus that occurred in and around a village called Luebo, along the Lulua River, in a southern province of the Democratic Republic of the Congo. Between late May and November 2007, more than 260 people sickened with what seemed to be or (in some confirmed cases) definitely was Ebola virus. Most of them died. The lethality was 70 percent. Leroy and his colleagues arrived in October, as part of an international WHO response team in cooperation with the DRC’s Ministry of Health. Leroy’s study focused on the network of transmissions, which all seemed traceable to a certain fifty-five-year-old woman. She became known, in their report, as patient A. She wasn’t necessarily the first human to get infected; she was merely the first identified. This woman, elderly by Congo village standards, died after suffering high fever, vomiting, diarrhea, and hemorrhages. Eleven of her close contacts, mainly family, who helped care for her, sickened and died too. The outbreak spread onward from there.
Leroy and his group wondered how the woman herself had gotten infected. No one in her village showed symptoms before she did. So the investigators broadened their search to surrounding villages, of which there were quite a few, both along the river and in the forest nearby. From their interviews and their legwork, they learned that the villages were interconnected by footpaths, and that on Mondays the heavy traffic led to one particular village, Mombo Mounene 2, the site of a big weekly market. They also learned about an annual aggregation of migrating bats.
The bats generally arrived in April and May, stopping over amid a longer journey, finding roost sites and wild fruit trees on two islands in the river. In an average year, there might be thousands or tens of thousands of animals, according to what Leroy’s group heard. In 2007, the migration was especially large. From their island roosts, the bats ranged the area. Sometimes they fed at a palm oil plantation along the river’s north bank; the plantation was a leftover from colonial times, now abandoned and gone derelict, but still offering palm fruits in April on its remaining trees. Many or most of the animals were hammer-headed fruit bats (Hypsignathus monstrosus) and Franquet’s epauletted fruit bats (Epomops franqueti), two of the three in which Leroy had earlier found Ebola antibodies. While roosting, the bats dangled thickly on tree branches. Local people, hungry for protein or a little extra cash, hunted them with guns. Hammer-headed bats, big and meaty, were especially prized. A single shotgun blast could bring down several dozen bats. Many of those animals ended up, freshly killed, raw and bloody, in the weekly market at Mombo Mounene 2, from which buyers carried them home for dinner.
One man who regularly walked from his own village to the market, and often bought bats, seems to have suffered a mild case of Ebola. The investigators eventually labeled him patient C. He wasn’t a bat hunter himself; he was a retail consumer. During late May or early June, according to patient C’s own recollection, he weathered some minor symptoms, mainly fever and headache. He recovered, but that wasn’t the end of it. “Patient C was the father of a 4-year-old girl (patient B),” Leroy and his team later reported, “who suddenly fell ill on 12 June and died on 16 June 2007, having had vomiting, diarrhoea, and high fever.” The little girl didn’t hemorrhage, and she was never tested for Ebola, but it’s the most plausible diagnosis.
How had she contracted it? Possibly she had