Militia violence in Democratic Republic of Congo (DRC) has prevented aid workers from reaching some suspected cases in an outbreak of Ebola that has so far took lives of 44 people, the World Health Organization (WHO) said.

At least 1,500 people are in high risk group exposed to the deadly virus in North Kivu province but the violence there prevents the officials from adequate measures to identify all the chains by which it is spreading in the east of the country.

“We don’t know if we are having all transmission chains identified. We expect to see more cases as a result of earlier infections and these infections developing into illness,” WHO spokesman Tarik Jasarevic said at a news briefing in Geneva.

“The worst-case scenario is that we have these security blind spots where the epidemic could take hold that we don’t know about,” he said.

The WHO, using figures compiled with Congo’s Health Ministry, said confirmed and probable cases numbered 78 in total, including 44 deaths. About 1,500 people have been identified as contacts of infected  patients transmitting the disease, which causes fever, vomiting and diarrhea.

The outbreak is spreading across the lush farmlands of eastern Congo. Its epicenter is the town of Mangina in North Kivu province and it has already reached neighbouring Ituri province.

Congo has experienced 10 Ebola outbreaks since the virus was discovered on the Ebola River in 1976, and it has altogether took away some 900 lives, according to registered cases.