BUNIA, Congo (AP) — Dozens of Congolese health workers at the epicenter of the fastest-growing Ebola outbreak on record staged protests Thursday to demand payment for their wages, abandoning several health facilities even as aid workers warn that the disease is still spreading at an alarming rate.

Confirmed cases in the outbreak, meanwhile, reached 3,973, including 1,801 deaths, according to the government data as of Tuesday published on Thursday. It is the second-largest Ebola outbreak on record, behind the 2014-2016 West Africa outbreak that recorded more than 28,000 cases, including over 11,000 deaths.

The health workers are protesting at the governor’s office in Bunia, the capital of Ituri province, which accounts for nearly 90% of the Ebola cases in the country. They are the latest group to walk off their jobs since protests over pay issues began weeks ago.

The health workers, including nurses providing critical care to Ebola patients, said they haven't received wages and bonuses for their work fighting Ebola since the outbreak was declared in mid-May in one of Congo’s most remote and vulnerable areas ravaged by rebel conflict.

“With this way of managing things, Ebola will not end in this province. We ask the authorities to get involved at all levels so that a solution is found quickly,” said Edouige Makosi, one of the protesters.

Officials have in the past blamed logistical issues for the payment delays. Congolese authorities did not immediately respond to an inquiry for comments on Thursday.

Poor welfare for frontline workers has been a key source of concern in the outbreak. Apart from the payment issues, many health workers and facilities have been attacked by rebels and angry mobs.

During his visit to Congo on Wednesday, World Health Organization Director-General Tedros Adhanom Ghebreyesus urged authorities to prioritize care and support for the responders.

The medical charity Doctors Without Borders said this week that the outbreak is still “spreading at an alarming and unprecedented rate” and that the response which has been expanding with more steps “is still not reaching communities quickly enough to break transmission chains.”

Government data shows 674 patients are currently in isolation, most of them in Ituri.

At least 75% of contacts being traced after their exposure to patients, the data showed. A bigger concern, though, according to officials, is that 60-70% of the new cases are coming from outside of those contacts, and are mostly from remote localities where rebel conflict and mining-related movements are limiting access.