FILE - In this file photo dated Wednesday, Aug 8, 2018, a healthcare worker from the World Health Organization prepares to give an Ebola vaccination in Mangina, Democratic Republic of Congo. Armed assailants attacked an Ebola treatment center in Butembo, in the heart of eastern Congo’s deadly outbreak on Saturday March 9, 2019, with the mayor reporting one police officer killed. (AP Photo/Al-hadji Kudra Maliro, FILE)

LONDON (AP) — The World Health Organization says Ebola has spiked in Congo in recent days because of "increased security challenges," a week after its director-general predicted the outbreak might be contained within six months.

The U.N. health agency said in an update late Thursday the recent attacks on Ebola clinics slowed response efforts for days. Congolese officials reported dozens of new suspected and confirmed cases recently. Last week, WHO chief Tedros Adhanom Ghebreyesus declared the outbreak was "contracting" and praised the efforts to avert a larger crisis.

Tariq Riebl of the International Rescue Committee, who is currently working in Congo, had a starkly different perspective.

"I think all of us in the field are aware that we're very far from being near the end of this outbreak," he said. Riebl said the recent jump in cases also points to ongoing surveillance failures.

"The increase in cases also shows we are catching up with all the transmission that we haven't previously been aware of," he said.

In recent weeks, more than 40 percent of new cases in the hotspot towns of Katwa and Butembo had no known links to other cases, meaning doctors have lost track of where the virus is spreading.

WHO reported this week that many people with Ebola are refusing to seek care in health clinics and are dying at home, further increasing the chances of transmission, since the bodies of victims are highly contagious.

Outbreak responders have also been targeted by rebel attacks; Doctors Without Borders was forced to shut down two of its Ebola clinics in Eastern Congo after repeated attacks and has called conditions at the epicenter "toxic." Eastern Congo is home to numerous armed groups and the Ebola epidemic has deepened the political and economic grievances of many in the area.

WHO teams often visit communities with a police escort for security reasons, a move that some think could undermine community trust.

"We understand why some people might be scared of this and we believe that the use of force should be a last resort," Riebl said, adding that IRC doesn't use armed escorts.

He noted that the outbreak would soon hit 1,000 cases; it is already the second deadliest Ebola outbreak in history. To date, there have been 915 confirmed cases, including 610 deaths.

"It's a sad threshold to reach, but it should also be a time of reflection," Riebl said. "We will not be able to stop this outbreak without local support."

Tedros Adhanom Ghebreyesus, Director-General of the World Health Organization (WHO), speaks at the European headquarters of the United Nations in Geneva, Switzerland, Thursday, March 14, 2019 about the update on WHO Ebola operations in the Democratic Republic of the Congo (DRC). (Martial Trezzini/Keystone via AP)
WHO Director-General, Dr Tedros Adhanom Ghebreyesus visits an Ebola treatment centre in Butembo, in the Democratic Republic of the Congo, Saturday March 9, 2019. Armed assailants again attacked an Ebola treatment center in the heart of eastern Congo's deadly outbreak on Saturday, with one police officer killed and health workers injured. (Dalia Lourenco/WHO via AP)