France, Oct. 18 -- The DRC's worst-ever Ebola outbreak has now passed the 9,000-case mark, with the number of deaths topping 4,000 at the beginning of this month.

Among the many challenges is the lack of any approved vaccines or treatments for the Bundibugyo strain of Ebola that is behind the outbreak.

The first clinical trial of a potential vaccine is expected to begin by the end of October, World Health Organization experts said on Tuesday.

Ervebo, a vaccine already approved for use against the more common Zaire strain of Ebola, will undergo a full-scale human trial in the DRC to see if it offers any cross-protection against Bundibugyo.

Two vaccines specifically for Bundibugyo are also being developed, one by the University of Oxfor...