"We are now extremely concerned, that several factors may be coming together over the next weeks to months to create a potential ideal storm", said Dr Peter Salama, WHO Deputy Director-General for Emergency Preparedness and Response.
Dr. Peter Salama said the response to the deadly hemorrhagic fever is at a "critical juncture" in eastern North Kivu province, where the outbreak was declared almost two months ago.
Overnight on Monday, unidentified assailants entered the town of Oïcha, about 20 km (12 miles) north of Beni, burned houses, killed one man and kidnapped 14 children and one woman, according to two local officials. An additional 31 deaths have occurred among probable and suspected cases, which would bring total Ebola deaths to 100 once confirmed.
The outbreak, the 10th in DRC's history, has killed 100 people since being declared on August 1 in the eastern part of North Kivu, the World Health Organization said.
In a second tweet, Salama communicated that the Ebola response teams in the city of Beni were on lockdown beginning Sunday.
The attack spurred the government to declare a "ville mort", or period of mourning, "out of respect for the victims" that will last until this Friday, effectively forcing aid groups to suspend their efforts to monitor and combat the outbreak. "An added complication here is that some of these fighters may have been exposed to Ebola, and yet they'll be even more hard to track down than ordinary civilians".
"Politicians in the region are also stoking the mistrust ahead of upcoming elections in December, " the Australian epidemiologist added. Congo's ministry of health has gained a reputation for being particularly adept at containing the disease, but many factors in this current outbreak make that hard. Rwanda, South Sudan and Burundi also border the region.