Birth of Ebola

We're all getting a crash course on the Ebola virus since it arrived in the US soon after the record outbreak in West Africa. What we haven't heard is the virus's origin. Scientists had believed Ebola was rather new at just ten thousand years old. But fossils reveal it appeared between sixteen and 23 million years ago, maybe earlier.

Ebola is member of the filoviruses that includes a similar virus, Marburg which has already caused several outbreaks in Africa. There are five strains of Ebola, of which only one does not cause human disease. Two Ebola strains caused outbreaks in 1976, the year we first identified it. Ebola Sudan, deadly half the time, occurred in Southern Sudan. Ebola Zaire, ninety percent deadly, took place in what's now the Democratic Republic of Congo and is behind the current outbreak.

To find Ebola's origin, scientists looked for pieces of Ebola and Marburg genetic information in animal fossils. They examined the genomes of two voles and two hamsters and found the same genetic pieces of the viruses in the same locations of both species. This suggests the viruses had infected a common ancestor of these rodents sometime before the Miocene Epoch, 23 million years ago. The viral genetic element also resembles more Ebola than Marburg suggesting the two viruses had already diverged by then. So, again, the virus is as old as the Miocene Epoch, possibly older.

Understanding Ebola's evolutionary biology isn't just interesting, it can help scientists as they create vaccines not just for Ebola Zaire but for the entire Ebola family of viruses.