The Democratic Republic of Congo has confirmed the first case of Ebola in the eastern city of Goma - a major transport hub with the population of more than two million.
It has raised fears the virus could spread across the border and infect Rwanda.
The World Health Organization says the case could be a "game changer".
The Congolese health ministry announced that a pastor tested positive after arriving in Goma.
More than sixteen-hundred people have died since this latest Ebola outbreak began a year ago.