Congo said on Thursday that Ebola had reached three new health zones, bringing the outbreak total to 676 confirmed cases and 136 deaths. The outbreak has also crossed into neighboring Uganda.

“There are still many blind spots in some areas that are high risk,” Olivier le Polain, a WHO epidemiologist based in Beni, eastern Congo, said.

Le Polain said surveillance systems needed to be strengthened in affected regions, adding that a shortage of isolation beds remained a major challenge. Only 250 beds were available across the three affected provinces, he said.

The outbreak involves the rare Bundibugyo strain of Ebola, for which there is currently no approved treatment or vaccine. Health workers said the disease went undetected for weeks, leaving responders struggling to contain its spread.

The WHO has not yet issued projections on the possible scale of the outbreak, Le Polain said.

The warning came after the US Centers for Disease Control and Prevention said the outbreak could potentially reach levels comparable to the 2014-2016 Ebola epidemic in West Africa, which killed more than 11,000 people.

Health officials said efforts to control the current outbreak are being complicated by limited medical resources and challenges in identifying cases early.