As viruses go, Ebola has a grim star power. When a new outbreak hits, Ebola kills a high fraction of its victims, causing horrific bleeding along the way. The latest outbreak started in March in Guinea. As of today, the World Health Organization reported 231 cases and 155 deaths.

In order to better treat Ebola, Pardis Sabeti of Harvard and her colleagues have been analyzing the virus’s evolution. It turns out that Ebola is not some freakish new plague, but rather old. If that seems puzzling, a research scientist in Sabeti’s lab, Stephen Gire, has created this animation, which I’ve embedded below, to explain it.

Gire’s video is part of a contest being run by the National Institutes of Health.