At least 500 people have died out of over 1,500 confirmed cases in the Democratic Republic of Congo's Ebola outbreak, authorities reported. The outbreak, declared on May 15, has recorded 1,561 cases, including 506 deaths, according to the latest update from Congo's Ministry of Health.

Frontline workers in Ituri province, the epicenter of the outbreak, issued a 24-hour notice on Sunday threatening to strike if their demands for payment and improved working conditions are not met. These workers, primarily health professionals, have been laboring with minimal rest while contending with attacks from skeptical residents and ongoing challenges in combating the virus.

A notice seen by The Associated Press indicated that workers both inside and outside hospitals have not received their benefits since the outbreak began and are lacking adequate supplies for their work. They also cited low salaries, perceived arrogance from teams dispatched from the capital, Kinshasa, and the disproportionate use of labor from other provinces without prioritizing local hires.

The strike threat emerges shortly after the commencement of clinical trial enrollments, raising concerns about the potential impact on containment efforts. A strike could further hinder attempts to slow the spread of the outbreak, which has now been confirmed in three eastern provinces: North Kivu, South Kivu, and Ituri.

Response efforts have been complicated by the lack of approved vaccines or treatments for the Bundibugyo virus, responsible for this particular outbreak. This differs from the more common Zaire virus, for which a vaccine exists and was responsible for most of Congo’s previous 16 Ebola outbreaks.

Officials are still working to identify the initial source of this outbreak, known as patient zero, and are tracing potentially tens of thousands of individuals who may have come into contact with infected persons. The World Health Organization has stated that the first month of this Ebola outbreak was the worst on record.