More than 500 people have died from Ebola in the Democratic Republic of Congo, where over 1,500 cases have been confirmed, as frontline healthcare workers threatened to begin a strike Monday over unpaid benefits and poor working conditions.

According to the Ministry of Health’s latest update released Sunday night, the outbreak has recorded 1,561 confirmed cases and 506 deaths since it was officially declared on May 15th.

Authorities say the virus continues to spread faster than response efforts can contain it.

Health workers in Ituri province—the epicenter of the outbreak—issued a 24-hour strike notice on Sunday, warning that they would stop working unless the government pays outstanding benefits and improves working conditions.

The workforce which is made up primarily of healthcare professionals, has been operating under intense pressure with little rest while responding to the outbreak. In addition to treating patients, many have faced hostility from frustrated residents and widespread public skepticism about the virus.

In a notice addressed to the government, obtained by The Associated Press, workers from both hospitals and community health teams said they had not received their benefits since the outbreak began. They also reported shortages of essential medical supplies needed to carry out their duties safely and effectively.

The strike threat comes only days after enrollment began for clinical trials in the outbreak zone, raising concerns about the potential impact on response efforts. Any work stoppage could significantly hinder attempts to contain the virus, which has now spread across three eastern provinces.

The World Health Organization has warned that the first month of this Ebola outbreak was already the worst on record, underscoring the urgency of strengthening the response before the crisis escalates further.