BUNIA, Congo (AP) — Congo’s authorities said Monday that the fastest-growing Ebola outbreak in history has topped 6,000 cases with 2,911 deaths.

More than 1,360 people have recovered from the virus, in what authorities said was an “encouraging” development.

The outbreak in eastern Congo is spreading under extremely difficult conditions, fueled by insecurity, displacement, a health workers’ strike and intense population movements. Last week, the virus has spilled into two new health zones in the region.

The World Health Organization has said that it remains out of control and is on track to surpass the 2014-2016 West Africa Ebola outbreak, the deadliest on record, which killed more than 11,000 people, primarily in Guinea, Liberia and Sierra Leone.