Ebola control measures seem to be working in Congo, WHO says

• Congo's Ebola outbreak not yet stabilized, WHO chief says

• 'Ray of hope' for Ebola patients as 2 given experimental treatment recover from virus

A previous outbreak in Congo this year was swiftly stopped,despite the remote location and difficult terrain.

The latest outbreak presents a different challenge,occurring in a more densely populated area with dozens of armedgroups. Some areas are off-limits to healthworkers due to thesecurity risks, making it more difficult to ring-fence eachEbola case by vaccinating all the patient's contacts.

On Wednesday WHO chief Tedros Adhanom Ghebreyesus said itwas too soon to say whether the outbreak was stablizing due tothe difficulty of identifying new cases near rebel-controlledareas.

"Substantial risks remain, posed by potential undocumentedchains of transmission," Friday's WHO statement said, addingthat four of the 13 new probable and confirmed cases in the pastweek were not known to have had contact with any Ebola patients.

There were also risks from unsafe burial practices andpeople's reluctance to accept contact tracing, vaccination andhealthcare, as well as poor standards in some health centres anddelays in getting patients to treatment.