South Korea on Ebola alert
A health worker prepares a sample taken from the body of an Ebola victim. Reuters

The head of the United Nations' Ebola response operation in West Africa has said that there remains a "huge risk" that the deadly virus could spread around the world.

In an interview with the BBC in Sierra Leone's Freetown, Tony Banbury said it is vital to "get down to zero cases" as soon as possible to prevent the disease reaching areas outside of West Africa.

"There is a huge risk to the world that Ebola will spread. It may spread around this sub-region, or someone could get on a plane to Asia, Latin America, North America or Europe... that is why it is so important to get down to zero cases as quickly as possible".

"Early on we adopted a strategy to get this crisis under control which involves treatment centres, safe burials and community mobilisation. That strategy is working," he said.

"But in some areas, including here in Sierra Leone - especially in the capital Freetown and in the town of Port Loko - we are falling short. And it is in those areas where we really need to focus our assets and our capabilities".

In October, he told the UN Security Council that "70% of all those infected by the disease must be under treatment and 70% of the victims safely buried if the outbreak is to be successfully arrested".

He confirmed that this target was being reach in "the vast majority" of areas in Guinea, Sierra Leone and Liberia.

Over 6,000 people have died from the virus and 16,000 cases have been reported, according to the World Health Organization (WHO).