(Bloomberg) -- Ebola treatment centers in eastern Democratic Republic of 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.

Since the outbreak was declared on May 15, there have been 676 confirmed Ebola cases, including 136 deaths in the DRC, according to the WHO

The country's health ministry said that spike also reflects more active surveillance