A female British healthcare worker has been diagnosed with Ebola in Sierra Leone, authorities in London said Wednesday, and a military plane has been sent to evacuate her if needed.

"We can confirm that a UK military healthcare worker in Sierra Leone has tested positive for Ebola," said a spokesman for Public Health England (PHE), a government agency.

The health worker is being treated in a specialist Ebola centre in Kerry Town in Western Sierra Leone.

A Royal Air Force plane has been sent to the country to be ready to evacuate the patient if needed.

"Medical experts are currently assessing the situation to ensure that appropriate care is delivered," the PHE spokesman said.

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

An estimated 700 British servicemen and women have been deployed to Sierra Leone to help in the response against Ebola, which swept through west Africa last year.

They have helped build and staff medical centres, along with a number of volunteers from Britain's state-run National Health Service.

Two British nurses, Pauline Cafferkey and William Pooley, contracted Ebola but recovered after treatment in Britain.

PHE said an investigation was underway into how the unnamed military worker caught the virus, and anyone in recent contact with the patient was being traced.

"Any individuals identified as having had close contact will be assessed and a clinical decision made regarding bringing them to the UK," the spokesman added.

Almost 24,000 people have been infected with Ebola since December 2013, almost all in Guinea, Liberia and Sierra Leone, and more than 9,800 have died, according to the World Health Organization.

Liberia last week discharged its last confirmed Ebola patient from hospital. No new case has been registered in the country since February 19.