A concerning outbreak of Ebola in Africa is growing larger and deadlier. And now, an American in the area has tested positive for the viral disease. Officials from the Centers of Disease Control and Prevention reported the American case over the weekend, involving a doctor working for a medical missionary group in the Democratic Republic of Congo. The doctor has been airlifted to Germany for treatment. There are now over 500 suspected cases and more than 100 suspected deaths linked to the outbreak, according to the World Health Organization. “We have significant uncertainty about the number of infections and how far the virus has spread,” said WHO representative Anne Ancia in a press briefing Tuesday. Out of nowhere Reports of a cluster of unexplained illnesses in the DRC first emerged in early May. On May 15, DRC officials officially confirmed the outbreak, though it had already grown quite large by then, with roughly 250 suspected cases. By May 16, the WHO declared a public health emergency of international concern over the outbreak—notably the first such declaration made by the WHO without seeking advice from an outside expert committee.

The majority of suspected or confirmed cases have been detected in the DRC, but there have been two imported cases identified in the bordering country of Uganda. The first known cases occurred in Bunia, the capital city of the DRC’s Ituri province, but it is not clear yet whether these represent the origin of the outbreak. As of May 19, only 30 or so cases have been confirmed.