The worst Ebola outbreak in recorded history has now infected 10,000 people, killing nearly 50 percent of them, the World Health Organization revealed on Saturday.

The number of "confirmed, probable and suspected cases" has reached 10,141, with 4,922 reported deaths, stated the W.H.O., which is tasked by the United Nations with directing the international responses to epidemics. Approximately 200 new cases are noted by the organization since its last report four days ago.

The west African countries of Guinea, Liberia, and Sierra Leone are by far hardest hit, accounting for all but 10 deaths and 27 infections. In addition to these nations, Mali, Spain, and the United States are listed as "affected countries," while Nigeria and Senegal are described as "previously affected countries."

Four hundred fifty health care workers are known to have contracted the disease, the vast majority of them in Guinea, Liberia, and Sierra Leone. In total, 224 health care workers have died from the virus, the report states.

However, these statistics likely under-count infections and deaths, because the outbreak has proven difficult to track in the most affected countries, due to poor medical treatment and testing services, as well as reluctance or inability of people to seek care.

Voices from west Africa to the United States have warned that austerity and "structural adjustment" programs have left medical systems ill-equipped to deal with the public health crisis.