It has been nearly 30 years since Ebola virus was identified during 2 outbreaks in the Democratic Republic of Congo (DRC) and Sudan [1, 2], and it has been closer to 40 years since Marburg virus, the first identified member of the filovirus family, was discovered [3, 4]. Despite investigators' considerable effort, the ecology of the filoviruses remains arguably as obscure today as it was after these first outbreaks. The article by Leroy et al. [5] makes a small step toward a better understanding of this ecology. Their study supports what many have suspected: that the filoviruses circulate widely in the central African rain forests and that they can infect humans and many nonhuman primates, including some previously undocumented members, such as mandrills and baboons (previously infected only in the laboratory). Although the recent outbreaks of Ebola in chimps and gorillas have created substantial additional concern for these already endangered species [6], the data in the Leroy et al. article show that the virus has been circulating in these populations, perhaps on a regular basis. The authors claim that Ebola is not necessarily lethal in these primates, but the infecting Ebola virus strain and its virulence remain unclear.We have known since the original Marburg outbreak that filoviruses could infect primates, because Marburg virus was first discovered in infected Circopithecus aethiops monkeys shipped from Uganda [7]. We also know that Marburg infections in humans have been seen from central to southern Africa and are possibly ongoing in eastern DRC [8–12], but we know virtually nothing of the ecology of the Marburg or Ebola strains in that or any other geographic area.