Ebola treatment centers in eastern Congo are becoming overwhelmed as confirmed cases surge past 800 and health workers struggle to track transmission chains, aid groups warned ahead of an emergency summit of African leaders.

A month after the outbreak was declared, surveillance, testing and contact tracing are struggling to keep pace with transmission in eastern Congo, where conflict and displacement have left almost 1 million people uprooted, health officials and aid groups said.

Congo’s National Institute of Public Health reported 808 confirmed cases and 192 deaths Monday, while Uganda has confirmed 19 infections. Ituri province, where the outbreak first emerged, accounts for more than 90% of cases in Congo.