Deaths in Congo's Ebola outbreak have passed 5,000, government data shows, the Associated Press and Reuters reported. The outbreak is caused by the rare Bundibugyo virus and was declared in May.

Health ministry data shows the disease has killed 5,026 of the 10,351 people infected, a death rate of nearly 50%, the AP reported. So far, 2,788 people have recovered, the AP said.

The virus has reached eight of Congo's 26 provinces, the two outlets reported. It has spread to 67 of the country's 178 health zones, the AP said. Ituri and North Kivu provinces in the east remain the center of the outbreak, with 9,782 confirmed cases and 4,792 deaths, according to the AP.

"It is a very tragic milestone because it is just not a number," said Dr. Patrick Otim of the World Health Organization, the AP reported. Otim said one-third of deaths happen outside treatment centers, before people are tested. The Africa Centers for Disease Control and Prevention said about 80% of new cases come from people outside known contact lists, the AP reported.

There are no approved vaccines or treatments for the Bundibugyo virus, Reuters reported. Only the 2014-2016 outbreak in West Africa, which killed more than 11,000 people, has been worse, the two outlets said.

Conflict and unrest in eastern Congo have slowed the response, the AP reported. On Friday, workers at an Ebola treatment center in Tchomia, in Ituri, stopped work to demand four months of unpaid wages, the AP said.

The outbreak has also spread beyond Congo. Kenya has confirmed eight cases and two deaths, the AP reported. Nigeria became the fourth African country to report a case last week, Reuters reported. Nigeria's one patient was taken to Switzerland for care, the AP said.

What we know: More than 5,000 people have died, and the virus has spread to other countries.
What we don't: When the outbreak will slow, with most new cases coming from unknown sources.