The Democratic Republic of Congo continues to make noteworthy gains in the fight against Ebola, though the health agencies face a challenge reaching militant infested regions and refugees fleeing clashes in the country, the World Health Organization said on Thursday.

There were only 14 confirmed cases in the past week, the lowest figure in a year and a drop from 51 in mid-September, and 126 in April – the peak of the outbreak.

"The fact that it is a smaller area is positive but the disease has also moved into more rural and more insecure areas," Dr Michael Ryan, executive director of WHO's health emergencies programme, said upon on his return from a trip to Congo.

"The virus is essentially back where it began." he said.

The current Ebola outbreak in the DR Congo has killed more than 2,100 people since August last year, and is considered the country's largest ever outbreak.

The World Health Organization reports that some 1,000 people have recovered from the disease, with more than 3,150 cases overall.

The agency in July declared the Ebola outbreak a public health emergency of international concern, calling for more measures to curb its spread.

Dr Ryan said the outbreak was confined to a geographic triangle stretching between the towns of Mambasa, Komanda, Oicha and Mandima, though it was still spreading at a low level.

"We are really reaching a point where we are more and more on top of things, more and more on top of surveillance, more and more on top of infection prevention and control," Ryan said. "The problem is it's back in areas that are deeply insecure." he said.

Congolese health authorities said last month that they plan to introduce a second Ebola vaccine, manufactured by Johnson & Johnson, to complement another single-dose vaccine made by Merck, but no date has been announced.