The World Health Organization raised the threat posed by Ebola in the Democratic Republic of Congo to “very high” as the virus spread in the African nation.

The epidemic is believed to have killed at least 200 people, though experts have warned of a significant undercount of both deaths and cases, pointing to contagion reported in the main regional hubs including in neighboring Uganda.

Fragile health systems, roiling intrastate conflicts, and attacks on treatment facilities have compounded the challenge of containing the virus. The new strain has also exposed health experts’ lack of preparedness for Ebola variants other than the common Zaire one. “Because of its rarity, [the Bundibugyo strain] just wasn’t on anybody’s radar,” a researcher told Bloomberg.