LONDON (AFP) - A British nurse who contracted the Ebola virus in Sierra Leone arrived in London by military plane on Sunday, the ministry of defence said.

The patient, who is not "seriously unwell" according to the Department of Health, is to be treated at an isolation unit at a London hospital.

The patient's bed will be sealed off with a tent with its own ventilation system. Only trained staff can enter the unit.

A spokesman for Sierra Leone's Ministry of Health, Yahya Tunis, said the man was a volunteer nurse working in Kenema in eastern Sierra Leone, one of the areas hardest hit by Ebola which has now been quarantined.

He is thought to be called William, according to British media reports

"His colleagues are very sad over the development as he is considered as a valued member," Tunis said, adding that he was involved in "surveillance, contact tracing and the burial of Ebola victims".

The Briton is the first person from the country to have contracted the virus in an outbreak that has killed at least 1,427 people in West Africa since March.

The Department of Health said the victim was evacuated in a specially equipped C17 Royal Air Force military plane to RAF Northolt in north west London.

The victim was to be taken in a special military ambulance to Britain's only specialist Ebola isolation unit at the Royal Free Hospital in London.

England's deputy chief medical officer Professor John Watson insisted that the risk of the virus being spread in Britain remained "very low".

"UK hospitals have a proven record of dealing with imported infectious diseases and this patient will be isolated and will receive the best care possible," he added.

Ebola spreads through direct contact with the blood or bodily fluids of an infected person.

The Ebola epidemic has spread through Liberia, Guinea and Sierra Leone, while Nigeria has also been affected. It is the worst-ever outbreak of the killer virus.

The World Health Organisation has warned it could take several months to bring the epidemic under control.