The Geneva-based body said Monday that the total number of confirmed, probable and suspected deaths from the disease comes from 20,656 cases in the three most affected countries a mortality rate of 39 percent.
The UN health agency says 2,915 deaths have been reported from Sierra Leone, 3,471 in Liberia and 1,767 in Guinea. The current outbreak, which began about a year ago, has also claimed more than dozen lives elsewhere.
The Ebola virus causes a form of hemorrhagic fever and is transmitted through bodily fluids such as blood, vomit or feces.