The Ebola outbreak in the Democratic Republic of Congo has surpassed 5,000 confirmed cases, with health officials warning that the virus is spreading at an unprecedented pace and remains far from under control.

Data from Congo’s Ministry of Health showed that 5,021 cases and 2,378 deaths had been recorded as of Sunday, making the outbreak one of the most severe Ebola crises ever documented.

The epidemic is unfolding in some of the country’s most difficult-to-reach areas, where insecurity, displacement and widespread population movement are complicating efforts to contain transmission.

Health officials say the current outbreak has infected and killed people at a faster rate than any previous Ebola outbreak. From the first detected case, the virus has spread roughly three times faster than during the 2014-2016 West Africa epidemic, which remains the deadliest Ebola outbreak on record with more than 11,000 deaths.

World Health Organization Director-General Tedros Adhanom Ghebreyesus warned Tuesday that the threat of further spread remains significant.

“The epidemic is far from being under control,” Tedros said, adding that the risk of further transmission both within Congo and internationally remains high.

Efforts to contain the outbreak have also been hampered by attacks on health workers, particularly in Ituri province, one of the areas hardest hit by the epidemic.

On Monday, residents in Aru territory reportedly attacked a health team following the identification of a suspected Ebola case. A mob set fire to an ambulance and damaged two other vehicles, according to Michael Wani, president of the Union of Cultural Associations for the Development of Ituri.

The violence adds another challenge for responders already struggling to trace contacts, isolate patients and provide treatment across remote and insecure communities.