GENEVA (AP) — The World Health Organization says there has been “a very dangerous and alarming development” in efforts to end the Ebola outbreak in eastern Congo, warning that the eruption of violence may re-ignite the epidemic.

Dr. Mike Ryan, who directs the U.N. health agency’s Ebola response, says there were only seven new cases last week. But he told reporters Friday that the near doubling of “security incidents” is jeopardizing attempts to end the outbreak.

He says officials have made progress in recent months but that “if security deteriorates in the region, we could work our way to a very bad situation.”

Ryan says WHO understands all the chains of Ebola transmission in this outbreak except one, a high-risk death with more than 300 contacts. Only a third have been followed.