West Africa is experiencing the worst ever outbreak of Ebola, the deadly virus that can kill up to 90 percent of those who contract it. Since this outbreak was first documented in February in Guinea, 635 people have been infected and nearly 400 have died, according to Reuters. So far, cases have been contained to Guinea, Sierra Leone, and Liberia, but a World Health Organization report out this week warned that neighboring nations should be prepared for outbreaks there as well.

Dr. Bart Janssens, director of operations at Doctors Without Borders (DWB), has said the problem is an epidemic that’s “out of control.” As the disease has spread, so has the fear of it. In April, a mob descended on a DWB treatment center in Guinea, accusing healthcare workers of bringing Ebola to the region.

However, the Reuters report also notes WHO hasn’t advised any travel or trade restrictions.