BUNIA, Congo — Health workers at an Ebola treatment center in eastern Congo went on strike Saturday over payment issues, disrupting care for patients in the epicenter of the country’s rapidly growing outbreak.

The number of confirmed cases of Ebola in Congo has reached 2,973, including 1,309 deaths, according to government data released Friday in what authorities say is the fastest-growing outbreak on record.

Activities at the Elikya Ebola Treatment Center in Bunia, Ituri province, were largely paralyzed after doctors, nurses and security staff stopped work.

About a hundred health workers protested outside the treatment center on Saturday. They said the unpaid bonuses were undermining morale and disrupting patient care, and called on Congolese authorities to settle the arrears so they could resume their work.

In a statement issued Friday, staff said they had unanimously voted to strike from Saturday until “concrete solutions” were found to resolve “two months of unpaid performance bonuses.”

Last week, health workers at Bunia General Hospital, the region’s largest medical center, went on strike over unpaid salaries. Some had told The Associated Press they have not received any payment since they started work at the onset of the outbreak.

The World Health Organization says more than 100 healthcare workers have been infected since the beginning of the outbreak.

The Central African nation has been battling the Ebola outbreak caused by the rare Bundibugyo virus since May 15. A total of 766 patients remain in isolation or in hospitals, while 540 have recovered so far, according to data from Congo’s Ministry of Health.

The eastern province of Ituri accounts for nearly 90% of confirmed cases.

The outbreak continues to spread faster than health officials can track despite an expanding response.

A key challenge is that health authorities have yet to identify the outbreak’s patient zero, while displacement from armed conflict and mining-related movements have made it difficult to trace thousands who have come in contact with infected individuals.

The response is being hampered by a funding gap, attacks on health centers, an ongoing conflict in eastern Congo and mistrust among local communities.

Response efforts have also been challenged by the lack of approved vaccines or treatments for the Bundibugyo virus, unlike the more common Zaire virus for which there is a vaccine and which was responsible for most of Congo’s past 16 outbreaks of the disease.

Enrollment in a highly anticipated study of two possible Ebola treatments recently started in Ituri.

The WHO says the global risk of the outbreak spreading outside Central Africa is low, noting Ebola spreads through direct contact with the bodily fluids of an infected person rather than through the air, making it much harder to spread than respiratory viruses.