EMBO Molecular Medicine

It’s widely believed that “patient zero” for the world’s deadliest Ebola outbreak was a two-year old boy from the remote village of Meliandou, Guinea. Like many children in his farmland town, the boy would play around and catch bats in the large hollow Cola trees that surrounded his small neighborhood. But in December 2013, the boy fell sick to a mysterious illness that would eventually kill him, and then spread to his family and neighbors. Months later, the disease, identified as Ebola, raced across West Africa, infecting 20,000 people and killing more than 7,800.

Now, researchers have found what they believe to be the very tree where the first contact between the boy and a virus-carrying bat occurred, setting off the devastating chain of events. A team of scientists from the Robert Koch Institute in Berlin visited Guinea in an attempt to understand how Ebola was transferred to humans. By interviewing the townspeople in the Meliandou village, the researchers learned of the large hollow tree filled with thousands of bats in which children would play. When they reached the tree, it was only a stump. The tree was burned months before, either as a coincidence or to protect the village, and charred bats rained down.

Bat-filled tree where 'patient zero' played
(EMBO Molecular Medicine)

Still, the researchers were able to glean crucial clues from the burnt stump. They found fecal DNA that belonged to long-tailed insect-eating bats that lived in the tree, they reported Tuesday in the journal EMBO Molecular Medicine. They believe the toddler who first died of the virus contracted it after playing in the bat-filled tree, either coming in contact with an infected bat or its fecal material. But because of the fire, which obliterated any definitive evidence, the team cannot be certain. “It’s probably the best we can get but we are very unhappy with the data,” Fabian Leendertz said to Scientific American.

Leendertz added that because they any infected bats most likely fled during the fire, his team’s research doesn’t prove the link between the insect-eating bats and the current Ebola outbreak. Other researchers agree. Peter Walsh, an Ebola researcher from the University of Cambridge in the United Kingdom, told Science that the finding is “suggestive, but it certainly doesn’t rise to a ‘smoking gun’ level.”

But even with the setback, the clues left by the tree may help exonerate fruit bats, which were widely thought to be the West African Ebola vector because they are hunted so often. The team’s findings also rule out larger mammals such as chimpanzees and antelopes as potential sources for the current virus outbreak, Leendertz said. Although identifying the type of animal that transmitted the Ebola virus to the young Guinean boy will do little to quell the current outbreak raging across West Africa, narrowing down the source could help scientists prevent similar epidemics in the future.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.