The head of the World Health Organization arrived in eastern Congo’s Bunia on Saturday, the epicenter of a rare and fast-spreading Ebola outbreak. Tedros Adhanom Ghebreyesus is scheduled to visit treatment centers and meet with health workers and affected families.

The WHO reports 906 suspected cases and 223 suspected deaths, though officials fear the true numbers are three to four times higher. Neighboring Uganda has confirmed nine cases and one death.

The current strain, the Bundibugyo virus, has no approved treatment or vaccine. The WHO last week upgraded its risk assessment to “very high” at the national level.

Response efforts remain outpaced by the spread. Doctors Without Borders warned this is one of the fastest-spreading outbreaks on record. Local anger over strict burial protocols has sparked at least three attacks on health centers. Rebel activity in Ituri, North Kivu, and South Kivu is also hindering access.

Uganda and Rwanda have closed their borders with Congo, but Tedros called such measures “not effective” and discouraged transparency. The U.S. has banned entry for non-citizens recently in Congo, Uganda, or South Sudan, and is conducting enhanced health screenings at major airports.