Scientists have traced the beginning of the current Ebola outbreak to a two-year-old boy named Emile Ouamouno, who lived in a small village called Meliandou in Guinea and died Dec. 2013. But how did the toddler get Ebola in the first place?
A small team of anthropologists, veterinarians and ecologists think they may have the answer. In a paper published Tuesday for the journal EMBO Molecular Medicine, lead author Fabian Leendertz of the Robert Koch Institute in Germany hypothesizes that Ouamouno got Ebola from a hollowed out tree where children in his community would often play. That tree, it turned out, was home to a large colony of free-tailed bats, which have survived experimental Ebola infection in previous research. That particular species of bat has also been discussed as a potential source for the virus in past outbreaks.
A photo from Leendertz's study.
Ebola is a zoonotic virus, which means that it can pass from animals to humans. In the past, Ebola outbreaks have been traced to bushmeat hunters killing and eating fresh meat from large primates. Leendertz and team ruled out that possibility for two reasons: one, usually the hunters themselves would be the first to come down with Ebola, and two, large primates are increasingly scarce and difficult to catch near Meliandou, according to villagers.
So instead Leendertz turned his attention toward fruit bats, another known Ebola virus carrier. But the fruit bat colonies were relatively far away from Ouamouno's village and besides, fruit bat hunters weren't the first to get sick with Ebola.
Finally, Leendertz focused on insectivorous bats, which children regularly hunted and grilled. He noted a large, hollowed-out tree stump about 55 yards from Ouamouno's home, along a well-trafficked path where women would walk on their way to a small river to do their washing. Villagers told Leendertz that children would often play in the hollowed-out tree, which turned out to be the home of a large colony of insectivorous bats.
A: The village of Meliandou. B–D: The burnt hollow tree; in (D), the arrow points at a stick, most probably left there by children.
Leendertz described the tree stump:
When we arrived, the tree had been mostly burned and only the stump and fallen branches remained (Fig 3C and D). Villagers reported that it burned on March 24, 2014 and that once the tree caught fire, a “rain of bats” started and a large number of bats were collected for consumption (see Materials and Methods). The bats were described as lolibelo, that is, small, smelly bats with a long tail. We found no evidence of additional zoonotic transmission events stemming from the consumption of these bats, but villagers reported disposing of them after a ban on bushmeat consumption was announced the following day.
Children would often capture these bats and play with them, writes Leendertz, and the first cluster of Ebola cases in Meliandou were mostly children and women, he notes, but because he wasn't able to test any of the bats that lived in the tree, there's no way to know for sure if they did indeed transmit Ebola to the little boy.
For now, he writes that his study is enough evidence to begin including insectivorous bats in Ebola outbreak analyses, where before scientists would point the finger at fruit bats or large primates. If Ouamouno is indeed the very first Ebola patient of this current outbreak, extra care needs to be taken to "avoid retribution attacks and stigmatization of the region," Leendertz cautioned. He also wrote that while the public needs to be informed of the risks of handling bats, they also need education about the "crucial ecosystem services" bats provide, which include benefits to humans.
So far in this Ebola outbreak, there have been 19,497 cases and 7,588 deaths, according to the latest figures from the World Health Organization.
A: In southeastern Guinea (Sierra Leone, Guinea, and Liberia are visible); scale bar stands for 50 km. B: In and around the index village, Meliandou; scale bar stands for 100 m.
To learn more about how the latest Ebola outbreak started, hear from father Etienne Ouamouno about how the virus destroyed his entire family in this video from the New York Times and Frontline (PBS). [Editor's note: there are conflicting reports about how old the toddler was when he contracted the disease. The New York Times reports he was one year old.]