The latest numbers show that Liberia last week reported its lowest number of new cases since early June, while Guinea and Sierra Leone both saw the fewest new cases since August.

"The decline is real, but that does not mean the fight is over," WHO spokesman Tarik Jasarevic on Thursday told adding that "this is a first optimistic sign."

A total 21,296 people have so far been infected with Ebola since the outbreak began just over a year ago, and 8,429 of them have died, according to the latest figures.

The three west African countries which account for all but 15 of those deaths, have dramatically scaled up the number of beds available in Ebola treatment centers and now count more than two treatment beds per case.

But the beds are unevenly distributed geographically, meaning all infected people are still not receiving treatment in some areas, the UN health agency acknowledged.

Ensuring treatment for all those infected with Ebola – one of the deadliest viruses known to man -- is important since it dramatically improves the chance of survival.

While 71 percent of all those infected with Ebola die, the fatality rate drops to 57 percent for those who are hospitalised, WHO said.

Under-reporting of Ebola deaths also means that not all burials of highly-infectious bodies are being conducted safely, despite sufficient capacity, it said.

WHO has acknowledged that the true number of Ebola deaths is likely far higher than the recorded figures, given that many deaths go unreported.

"It is vital that we reach the target of 100 percent safe burials," Jasarevic said. Liberia, which was long the hardest-hit country and still counts the most deaths at 3,538, has seen the clearest drop in transmission.

Only eight new cases were reported in the country during the week leading up to January 11, with no new cases in the final two days of the week, down from a peak of more than 300 confirmed cases per week in August and September.

In Guinea, where the epidemic began in December 2013 and which counts 1,814 deaths, 42 new cases were confirmed in the same seven-day period.

Sierra Leone, which currently has the most infections – 10,124, of whom 3,062 have died -- meanwhile counted 184 confirmed new cases during the week to Sunday, with 59 new cases in Freetown alone, WHO said.

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