The World Health Organization has declared a rare Ebola outbreak a public health emergency of international concern, with its chief warning that the number of suspected cases, currently at 600, and 139 suspected deaths, is expected to climb significantly. This grim forecast comes as the virus circulated undetected for some time before the outbreak was identified.

The World Health Organization on Sunday declared an Ebola outbreak in the Democratic Republic of Congo and Uganda a “public health emergency of international concern.”

More than 300 suspected cases and 88 deaths have been reported. The outbreak is caused by the rare Bundibugyo virus, which has no approved treatments or vaccines.

* Says at least 90 deaths recorded so far in DR Congo, Uganda

The Ebola disease, which the World Health Organization calls a severe, often fatal illness affecting humans and other primates, has claimed 130 lives as of May 19, according to…