The Ebola outbreak claimed nearly 200 lives in less than a week in West Africa and shows no signs of letting up, the World Health Organization announced Tuesday. Ebola has killed some 2,288 people in Guinea, Liberia and Sierra Leone since the outbreak began six months ago. Nearly half of those deaths occurred in the last 21 days, indicating the disease has begun to spread more rapidly, WHO said.

“The increase in cases continues to accelerate in countries with widespread and intense transmission,” the health agency said. Nearly 4,269 cases of Ebola have been reported.

The current Ebola outbreak began in Guinea, where 555 deaths have been reported, but most cases have occurred in Liberia, where some 1,224 people have died from the disease. There have also been 21 cases and eight deaths in Nigeria, and one confirmed case in Senegal. The majority of new cases were in Liberia and Sierra Leone. WHO released a map showing where new cases have been identified via its Twitter page. 

Just last week, the death toll from the outbreak, the deadliest in history, topped 2,000. WHO officials warned it could claim as many as 20,000 lives before it is over

Tom Frieden, director of the Centers for Disease Control and Prevention, has said the Ebola crisis is “spiraling out of control.”