The hollow Cola tree growing in a remote area of southeastern Guinea was once home to thousands of bats routinely hunted and killed by the neighborhood children. It was also a popular spot to play. A year ago, one child in particular lived within fifty meters of the tree: a two-year-old boy who died in December 2013 and later was identified as the first person in west Africa known to have developed Ebola. The tree was one of the few that loomed over his home village of Meliandou, a hamlet of 31 houses. The question that now haunts researchers: were the tree’s occupants behind how that small boy contracted the virus in the first place?