GENEVA (AP) — The director-general of the World Health Organization says recent attacks on Ebola treatment centers in Congo threaten to reverse the gains that have been made in fighting the epidemic.

Tedros Adhanom Ghebreyesus, who has just returned from a visit to eastern Congo, noted reports on Thursday of a new attack on an Ebola treatment center.

Tedros vowed that WHO and its partners will strike a balance between protecting patients and health workers, and building trust in communities.

Doctors Without Borders recently described conditions at the epicenter of the outbreak as "toxic," saying that government security forces were complicating the effort. Three Ebola centers have been attacked in addition to Thursday's report.

Congo's health ministry says 584 people have died in what is now the second-worst Ebola outbreak in history.