Re-admitted to hospital earlier this week following an “unusual late complication,” the hospital treating her said her condition has “deteriorated”.
The nurse, from South Lanarkshire, was admitted to the isolation unit at the Royal Free Hospital in London on Friday after becoming unwell in Glasgow.
A statement from the Royal Free said on Wednesday: “We are sad to announce that Pauline Cafferkey’s condition has deteriorated and she is now critically ill. She is being treated for Ebola in the high level isolation unit at the Royal Free Hospital.”
She had become unwell earlier in the week and was treated at the Queen Elizabeth University Hospital in Glasgow on Tuesday before being transferred. Her family claim doctors “missed a big opportunity” when she visited an out-of-hours clinic the day before but was sent home.
A total of 58 close contacts of the nurse have been identified – a combination of healthcare workers and friends and family – with 40 of those offered vaccinations as a precaution.
Pride of Britain
Days before the infection returned, Ms Cafferkey won an award at the Pride of Britain Awards in central London on 28 September.
She met the prime minister’s wife Samantha Cameron the following day at Downing Street, alongside other winners.
A report from the charity in February said she was probably infected as a result of using a visor to protect her face rather than goggles. It said she was unable to use the standard protective goggles because she could not get them to fit properly.
Ms Cafferkey’s temperature was tested seven times before she flew from Heathrow to Glasgow in December, and she had been cleared for travel