A London hospital says the condition of a British nurse being treated for Ebola is now critical after her health detoriated over the past two days.
The Royal Free Hospital has been treating Pauline Cafferkey with blood plasma from disease survivors and an experimental anti-viral drug, the BBC reported.
She was diagnosed with Ebola after returning to Glasgow from Sierra Leone late last month.
The virus has killed more than 7800 people, almost all in West Africa, since it broke out a year ago.
The World Health Organisation has said the number of people infected by the disease in Sierra Leone, Liberia and Guinea has now passed 20,000.
'It was kind of a natural thing'
Miss Cafferkey had flown out with a team from the charity group Save the Children.
Before she set off, she spoke to BBC Radio Scotland about her instinct to help those affected by the disease.
"To me, it was kind of a natural thing. I couldn't think of any reason why not to go," she said.
"Having experience in the past before - I've done aid work, I've worked in Africa. I didn't really think about it actually. I've just done it."
She had travelled home via Casablanca, Morocco and London's Heathrow Airport.
She was screened for the disease at Heathrow where she told officials she believed a fever might be developing.
Her temperature was taken seven times in total, six of which were within 30 minutes, and was normal each time, so she was allowed to fly home to Scotland.
The government's chief medical officer, Dame Sally Davies, has said the case raises questions about airport screening procedures.
Ms Cafferkey was later placed in an isolation unit in Glasgow after becoming feverish, before being transferred to London and on to the Royal Free's specialist treatment centre.
Risk to public 'almost nil'
Officials from Health Protection Scotland have spoken to all 71 people aboard the British Airways flight from Heathrow to Glasgow that Ms Cafferkey took - a Public Health England (PHE) spokeswoman has said.
All 101 UK-based passengers and crew aboard the Royal Air Maroc flight from Casablanca to Heathrow have also been contacted by PHE officials.
The remaining 31 international passengers on the flight were being traced by international health authorities, the spokeswoman added.
Dr Nick Beeching, an infectious disease specialist and a senior lecturer at the Liverpool School of Tropical Medicine, told the BBC the risk to the general public of disease spreading was "almost nil".
He said Ms Cafferkey was receiving the best possible care, and the doctors and nurses at the Royal Free were aware of the risks of contamination.
Ebola is transmitted by direct contact with the bodily fluids of an infected person, such as blood, vomit or faeces.