As of September 6, 2,288 people had died in Guinea, Sierra Leone and Libera out of 4,269 cases, the UN's health agency said.
A full 47 per cent of the deaths and 49 per cent of the cases had come in the prior 21 days, it said.
The countries bearing the brunt of the epidemic are among the world's poorest, with dilapidated medical infrastructures buckling under the strain.
Liberia has been by far the hardest hit by the epidemic, which since it began in neighbouring Guinea at the beginning of the year has ballooned into the deadliest Ebola outbreak the world has ever seen.
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WHO warned on Monday that Liberia would likely face "many thousands" of new infections in the next three weeks.
Guinea meanwhile counts 555 deaths, while the deadly virus has claimed 509 lives in Sierra Leone, WHO said.
Another eight people have meanwhile died in Nigeria out of 21 cases, while one case of Ebola has been confirmed in Senegal, WHO said.
On Friday, the UN agency had put the overall death toll from the raging epidemic in the five countries at 2,105 out of 3,967 cases.
That country, where the virus was first identified in 1976, said at the weekend that it so far had registered 32 Ebola deaths and 59 likely or confirmed cases.