LONDON (REUTERS) - Britain said on Wednesday a military health-care worker had tested positive for Ebola while working in Sierra Leone and a decision would be taken soon on whether the individual should return home for treatment.

"An investigation into how the military worker was exposed to the virus is currently under way and tracing of individuals in recent contact with the diagnosed worker is being undertaken," Public Health England said in a statement.

"A clinical decision on whether the individual will be medically evacuated to the UK for treatment will be taken in due course."

Two Britons who contracted the virus have already been successfully treated at the Royal Free hospital in London, the country's designated centre, and other health-care workers have also been treated there.

The British government has said hundreds of national health workers have volunteered to travel to west Africa and help those affected by the virus.

Ebola has now killed nearly 10,000 people in the three worst-affected countries of Guinea, Sierra Leone and Liberia, and infected more than 24,200 people since the outbreak began in Guinea a year ago.

Rates of new infections have come down swiftly in recent months, however, and Liberia last week released its last known Ebola patient from hospital.