U.S. officials say they are responding after an American tested positive for Ebola in the Democratic Republic of Congo, with President Donald Trump saying he is “concerned” about the outbreak during a White House event, according to CNBC.

The case comes as health authorities in Central and East Africa move to contain the Bundibugyo strain of Ebola, which the World Health Organization has classified as a public health emergency of international concern, though not a pandemic emergency.

Uganda has placed more than 100 people under quarantine as officials monitor possible exposure linked to the outbreak, Africanews reported.

Authorities said the contacts are being observed by experienced medical teams while the country strengthens public health precautions.

In the DRC, President Félix Tshisekedi has instructed the government to reinforce the Ebola response in Ituri and North Kivu, where suspected cases and deaths continue to be investigated, Radio Okapi reported.

U.S. officials said there are currently no Ebola cases in the United States and that efforts are focused on supporting Americans in the affected region while preventing any domestic spread.