Ebola toll tops 1,550 as outbreak accelerates, WHO says

Health workers, wearing head-to-toe protective gear, prepare for work, outside an isolation unit in Foya District, Lofa County, Liberia in this July 2014 UNICEF handout photo. As of July 27, 2014, a total of 1,323 cases, including 729 deaths, had been attributed to Ebola virus disease (EVD) in the four West African countries of Guinea, Liberia, Nigeria and Sierra Leone. Liberia has borne 329 of these cases, including 156 deaths. REUTERS/Ahmed Jallanzo/UNICEF/Handout via Reuters (LIBERIA - Tags: HEALTH) THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS. FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. MANDATORY CREDIT - RTR40Z0Y

The Ebola outbreak in West Africa has killed more than 1,552 people out of 3,069 known cases in four countries and "continues to accelerate", the World Health Organization (WHO) said on Thursday.

The epidemic in the region, the deadliest since the disease was first discovered in 1976, has killed nearly as many people as all the previous known outbreaks combined.

"More than 40 percent of the total number of cases have occurred within the past 21 days. However, most cases are concentrated in only a few localities," the United Nations health agency said in a statement.

The WHO is later due to launch a new strategic plan for tackling the spread of the virulent disease.

A separate Ebola outbreak in the Democratic Republic of Congo, identified as a different strain of the virus, is not included in the latest figures which cover Guinea, Liberia, Sierra Leone and Nigeria.

The disease has overwhelmed West Africa's already fragile health infrastructure. On Wednesday, the head of the African Development Bank said it was causing enormous damage to the economies of the region.