France, May 20 -- The World Health Organization (WHO) warned that the outbreak had spread undetected for weeks, with more than 600 suspected cases and 139 suspected deaths from the disease now recorded.

Infections have also appeared in neighbouring Uganda, raising concern over the spread of this rare Bundibugyo strain of Ebola, for which there are no approved vaccines or treatments.

Concern over the "scale and speed" of the outbreak was raised by WHO director-general Tedros Adhanom Ghebreyesus during a meeting in Geneva on Tuesday.

"Numbers are expected to rise, given the amount of time the virus circulated before the outbreak was detected," he said.

WHO declares global emergency as DRC Ebola outbreak spreads beyond borders Emergency ...