KINSHASA, Congo — The world’s fastest-growing Ebola outbreak is spreading faster than efforts to fight it, the head of the World Health Organization said on Wednesday during a visit to Congo where some health workers are striking over a lack of pay.

Nearly three months into the outbreak, new cases are doubling in some hot spots, Tedros Adhanom Ghebreyesus said in a post on X after meeting with officials in the capital, Kinshasa. It was the second visit by the WHO director-general to the Central African country since the outbreak was declared in mid-May.

“We all agree that we must urgently and massively scale up all our efforts across all pillars of the response and by all partners,” Tedros said.

The outbreak has accounted for 3,874 confirmed cases, including 1,751 deaths, as of Monday, according to the latest data from Congo’s Ministry of Health.

In Ituri province, the epicenter of the outbreak, families said many front line workers have gone on strike, worsening access to healthcare that was already challenged by rebel conflict in one of Congo’s most remote and vulnerable areas, its east near the borders of South Sudan, Uganda and Rwanda.

While some workers say they have started receiving payment in the last week for work done since the outbreak began, they are demanding improved wages.

Anicet Baluku, a resident of Bunia, the capital of Ituri, blamed the death of his two brothers from Ebola on the strike. “We urge the authorities to quickly find a solution to prevent other families from experiencing the same tragedy,” he told The Associated Press.

The U.S. Department of State said on Wednesday that it will provide an additional $242 million in funding for immediate Ebola response and preparedness efforts in the region and for humanitarian assistance related to the outbreak. Such funding, it said in a statement, has now exceeded $512 million in direct assistance.

The outbreak has eclipsed all previous Ebola outbreaks in its speed of transmission and is the second-largest outbreak on record, behind the 2014-2016 West Africa outbreak that recorded more than 28,000 cases, including over 11,000 deaths.

The Bundibugyo virus that is causing this outbreak has no approved treatment or vaccine, and local officials believe it began in a remote area long before it was declared on May 15.

The outbreak is still “spreading at an alarming and unprecedented rate,” the medical charity Doctors Without Borders said on Wednesday, adding: “The response is expanding but is still not reaching communities quickly enough to break transmission chains.”

Dr. Jean Kaseya, head of the Africa Centers for Disease and Control, said on Tuesday during a visit to Bunia that contact tracing isn’t working, with at least 60% to 70% of new cases coming outside of those being monitored after exposure to patients.

Late detection of cases has been a key contributor to the 45% fatality rate, officials say. Of the 77 most-recent cases reported during a 24-hour period, 44 were fatal, according to the health ministry. At least 717 patients are in isolation while 749 patients have recovered.

Kaseya, who met with Tedros on Wednesday, said Africa CDC is aligning its efforts with responders “around earlier detection, stronger contact tracing, rapid access to quality care and deeper engagement with communities.”

Tedros called for action to reach all affected localities, strengthen coordination under the government’s leadership and protect health workers.

“Above all, communities must be at the center of and have ownership of the response,” he said. “We cannot stop Ebola without their trust, leadership and partnership.”