LONDON (AFP) - A female British health-care worker who contracted Ebola in Sierra Leone was being flown home for treatment on Thursday, the Ministry of Defence (MoD) said.

A Royal Air Force plane sent to the west African country on Wednesday is bringing the military servicewoman back to be treated in London's Royal Free Hospital, an MoD spokeswoman said. The condition of the patient, who was publicly confirmed to have Ebola on Wednesday, is unknown.

She is the third Briton to contract the virus in Sierra Leone - two nurses, William Pooley and Pauline Cafferkey, recovered after being treated in Britain. The MoD spokesman said: "Despite there being stringent procedures and controls in place to safeguard UK service personnel, there is always a level of risk in deployments on operations of this type."

Public Health England, a government agency, has said that the risk to the British public was "very low".

Ebola has swept through Sierra Leone, Guinea and Liberia since December 2013, killing more than 9,900 people, according to the World Health Organization (WHO).

Britain has focused its aid effort on its former colony, Sierra Leone, and up to 700 British military personnel have been deployed along with numerous civilian medical staff.