Congo’s Ebola outbreak has surpassed 5,000 cases, with health officials warning that the virus is spreading at an unusually fast pace and putting pressure on response efforts in one of the country’s most remote areas.

Data from Congo’s Health Ministry showed that 5,021 cases had been recorded as of Sunday, including 2,378 deaths.

The outbreak is unfolding amid insecurity, displacement and large movements of people, making it difficult for health workers to contain the virus.

According to health officials, the outbreak has spread faster than any previous Ebola outbreak. From the first confirmed case, it has expanded about three times faster than the 2014-2016 outbreak in West Africa, which was the deadliest Ebola outbreak on record, killing more than 11,000 people.

World Health Organization Director-General Tedros Adhanom Ghebreyesus said Tuesday that the outbreak was spreading rapidly and that the risk of further transmission within Congo and beyond its borders remained high.

He warned that the epidemic was still far from being brought under control.

Security problems have also hampered response efforts, particularly in Ituri province, the area worst affected by the outbreak. Health workers have faced attacks while trying to investigate cases and provide treatment.

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