The virus has spread rapidly over the past 21 days, and the number of patients increased significantly.
WHO added that the infection continued to expand through Guinea, Liberia and Sierra Leone. Its incubation period is 21 days, which is why WHO conducts a new analysis every three weeks.
Until Sept. 6, Guinea had recorded 862 infections and 555 deaths. But over the 21-day period just concluded, there were an additional 339 infections and 155 deaths reported.
In Liberia, 2,064 infections were recorded, of which 1,224 resulted in the deaths of those stricken by the virus. The increase over the same time frame added 1,212 infections and 758 deaths to the mounting toll.
WHO said that it expects thousands of new infections during the upcoming three weeks in Liberia, where there is one doctor for every 100,000 people in a country with a population of 4.4 million.
In Sierra Leone, 1,361 were infected and 509 died, with an increase of 533 infections and 154 deaths.
Of the 4,269 cases recorded to date in those three countries, 2,048 of the infections occurred in the past three weeks. Regarding the total number of 2,228 deaths, 1,067 occurred in the same time frame.
In Nigeria, eight infections and four deaths were recorded in the past 21 days. The total toll there is 21 infections and eight deaths.
Three infections and no deaths were observed in Senegal, none of which happened in the past three weeks.
This is the biggest outbreak of the deadly Ebola since the virus was discovered in the Democratic Republic of Congo (then called Zaire), in 1976. There is no known cure for the infection, which has a high mortality rate.