A British military healthcare worker in Sierra Leone has tested positive for Ebola.
Public Health England (PHE) said the worker, who is reported to be female, is being assessed by medical experts while a decision is made about whether to bring them back to the UK.
The Ministry of Defence said the worker is currently being treated in the specialist Ebola treatment centre in Kerry Town.
Up to 700 British military personnel have been working in the west African country to aid the Ebola crisis.
British nurses Pauline Cafferkey and Will Pooley both survived the highly-contagious disease after contracting it while treating patients in Sierra Leone last year.
A PHE spokesman said: “We can confirm that a UK military healthcare worker in Sierra Leone has tested positive for Ebola. Medical experts are currently assessing the situation to ensure that appropriate care is delivered. A clinical decision on whether the individual will be medically evacuated to the UK for treatment will be taken in due course.
“An investigation in to 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.
“Any individuals identified as having had close contact will be assessed and a clinical decision made regarding bringing them to the UK.”
More than 9,960 people have died from the Ebola outbreak in West Africa, according to the latest figures from the World Health Organisation (WHO).
The outbreak has been raging for more than a year, with Sierra Leone, Guinea and Liberia being the worst affected countries where more than 24,000 confirmed and suspected cases have been reported.
But the epidemic has shown signs of slowing down in recent months and Liberia released its last Ebola patient from a treatment centre last week.
No British nationals have died and Mr Pooley and Mrs Cafferkey were the only Britons to have tested positive for the disease until today, although a number of others have been tested.
Among them were two other military healthcare workers, who were discharged from hospital last month after being kept under observation following needle-stick injuries while treating sufferers in Sierra Leone.
They, along with Mr Pooley and Ms Cafferkey, were treated in a specialist isolation unit at London's Royal Free Hospital (RFH).
Mr Pooley, from Eyke in Suffolk, tested positive for the virus while in Sierra Leone last August and was flown back to the UK by the RAF.
He has since returned to Sierra Leone to resume his work.
Ms Cafferkey, from Cambuslang, in South Lanarkshire, had volunteered with Save The Children at a treatment centre in Kerry Town in Sierra Leone and was not diagnosed with Ebola until after she returned to the UK in December.
She was discharged from the RFH in January.
The Ministry of Defence spokeswoman said: “A clinical decision on whether the individual will be medically evacuated to the UK for treatment will be taken in due course.
“Their next of kin have been informed and we will not be providing any further details at the current time.
“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”.
The PHE spokesman added: “The UK has robust, well-developed and well-tested systems for managing Ebola and the overall risk to the public in the UK continues to be very low.
“No further information is being given at this time.”
PA