The Ebola outbreak in the Democratic Republic of Congo is spreading southwards into an area with high security risks, according to the UN World Health Organization (WHO).

The outbreak has already killed 439 of more than 700 infected patients.  Controlling the spread of the killer virus is dependent on tracking where it goes by tracing people who may have had contact with the disease.  Unfortunately, it's spreading into a region of DR Congo with even higher levels of factional fighting than the areas already impacted.  That raises the difficulty level for health workers whose movements are restricted by the fighting, cutting them off from patients and from people who need instructions about how to avoid becoming sick.

There's an upside.  As the virus spreads south, there's been a decline in cases around the previous hotspot Beni.

"It is very premature to shout victory, it's true we had some success in Beni because all the steps we've taken have had an impact, but unfortunately we see cases turning up in other areas," said WHO spokeswoman Fadela Chaib.  "The country is not only facing Ebola but other health threats, just to name malaria, cholera, vaccine-derived polio, and also a very long humanitarian crisis and a lot of violence in several regions."

Experimental vaccines have been administered to 40,000 people in DR Congo, as well as 2,500 in Uganda.