Ebola spread to an eighth province in the Democratic Republic of Congo, Reuters reported, as health workers confront a heavy toll among young children, adding new challenges to efforts to contain the fastest spreading epidemic of the disease.

Two cases were confirmed in North Ubangi, a province bordering the Central African Republic, Reuters said Thursday, citing two health officials. The infections haven’t yet been officially announced by national authorities and would mark the first confirmed cases in the province.

The expansion comes as Doctors Without Borders, also known by its French initials MSF, warned that children are accounting for an out-sized share of infections in North Kivu, another province where transmission has intensified. Almost a quarter of confirmed cases there are among children younger than 5, more than half of whom are infants, according to MSF’s epidemiological research arm.

Many of the children may have contracted Ebola while receiving treatment for other illnesses in ordinary health facilities before being referred for specialized care, MSF said in a statement Thursday. At its Ebola treatment center in the town of Butembo, 24 of 30 children admitted with the disease between June and September died, most of them younger than 5.

Their family members didn’t have Ebola, making it “highly likely” that the children became infected in healthcare facilities, said Stéphanie Hoffmann, MSF’s project coordinator in Butembo.

The findings highlight weaknesses in infection control as the Bundibugyo Ebola outbreak, first declared in May, continues to spread. Congo had recorded 9,212 confirmed cases and 4,441 deaths as of Oct. 13, according to the government’s latest situation report, which listed seven affected provinces.