The World Health Organization (WHO) logo is pictured at the entrance of its headquarters in Geneva, Jan. 25, 2015. REUTERS/PIERRE ALBOUY

(Reuters) - West Africa's Ebola epidemic still poses a threat to other countries but the risk of it spreading internationally appears to be diminishing as the areas affected shrink, the World Health Organization (WHO) said on Friday.

The U.N. agency declared in August 2014 that the world's worst Ebola outbreak, which began in December 2013, represented a "public health emergency of international concern" that forced health officials worldwide to shore up defenses.

The WHO's Emergency Committee, comprising independent experts who conferred on Thursday, was "absolutely firm" in maintaining that view, said Dr. Bruce Aylward, WHO Special Representative for the Ebola Response.

In a statement, the Committee said that due to better prevention and control activities across West Africa, "the overall risk of international spread appears to have further reduced since January with a decline in case incidence and geographic distribution in Liberia, Sierra Leone and Guinea."

But there was "no place for complacency" and the goal remained eliminating the deadly hemorrhagic fever.

Thirty confirmed cases of the virus were reported in the past week, the smallest number in nearly a year, the WHO said on Wednesday. Liberia reported no cases in the week to April 5, Sierra Leone reported nine and Guinea 21..

The virus has killed 10,587 people out of 25,556 known infections, according to the WHO.

The outbreak's epicenter, in Guinea Forestiere, has "gone quiet" and foreign medical experts and laboratories are being shifted to coastal areas with more intensive spread, Aylward said.

"There are still substantive risks, they are not at zero (cases) by any stretch, but they may be now on track to achieve their goal of really being down to only disease in that coastal area by the time the rainy season hits in about a month.

The experts urged all countries to "avoid any unnecessary interference with international trade and transport".

These included border closures, flight cancellations, refusal of entry, and quarantining of travelers returning from the region, the statement said.

Some 40 countries still implement additional measures beyond the recommended health measures and a number of airlines have not resumed flights, it said.

Falling Ebola cases make completing big clinical trials on experimental vaccines a challenge, with the best hope resting on a study in Guinea, Aylward said. Last month, Guinea started testing an experimental vaccine from Merck and NewLink Genetics on affected communities.