A British man who contracted the Ebola virus in Sierra Leone has arrived back in the UK on board an RAF jet.

The healthcare worker landed at London's RAF Northolt in a specially-equipped C-17 aircraft and has been transported to an isolation unit at the Royal Free Hospital in north London, BBC reports.

The man is "not currently seriously unwell", a Department of Health spokesman said.

Health officials have stressed the risk to the UK remains "very low".

Prof John Watson, DoH deputy chief medical officer, said they would be taken in a specially-adapted ambulance to a high level isolation unit - the only unit of its kind in the UK.

It is the first confirmed case of a Briton contracting the virus during the current outbreak, in which 1,427 people have died.

The World Health Organization has estimated 2,615 people in West Africa have been infected with Ebola since March.

The unit at the Royal Free in the Hampstead area of London has been prepared to treat people with highly infectious diseases.