The Ebola outbreak in the Democratic Republic of Congo has become the third largest ever recorded and is spreading faster than health authorities can contain it, the World Health Organization warned on Tuesday. As of mid-July, at least 1,963 people have been infected and 719 have died across four provinces in eastern Congo, with the Bundibugyo strain — a rare type of Ebola for which no approved vaccine or treatment yet exists — driving the crisis. The Africa CDC has described it as the fastest-growing Ebola outbreak on the continent.

The most alarming indicator, according to WHO emergencies chief Chikwe Ihekweazu, is that 80% of new cases are emerging from unknown chains of transmission — meaning health workers have no prior contact records for the majority of those now falling ill.