Health authorities have confirmed more than 260 cases of the virus in the two countries and are investigating another 1,100 possible infections.

Over 40 people have died in a growing Ebola outbreak in the Democratic Republic of the Congo and Uganda, where government and international aid organizations are struggling to cope with the spread of the disease.

The current strain of Ebola, the Bundibugyo virus, is “a severe and often fatal form” of the disease, according to the World Health Organization. It has no approved treatment or vaccine.

The World Health Organization and the Africa Centres for Disease Control and Prevention both reported 43 confirmed deaths across the countries as of Saturday, including 42 in Congo and one in Uganda, according to the WHO. However, 349 people are suspected to have died from the virus in Congo and Uganda.