Ebola nurse Pauline Cafferkey's condition has improved to "serious but stable", according to hospital officials.

The 39-year-old was reported to be "critically ill" after her condition deteriorated last week.

A military plane flew her from Glasgow to London on 9 October after an "unusual late complication" caused her to fall ill again.

It was thought she had recovered from the virus.

She has been treated in the high level isolation unit at the Royal Free Hospital in London.

A statement from the Royal Free said: "We are able to announce that Pauline Cafferkey's condition has improved to serious but stable."

Ms Cafferkey contracted the disease after treating patients in Sierra Leone at the height of the outbreak which has killed more than 11,000 people.

She was first treated at the Royal Free Hospital in December and discharged in January.

The nurse from South Lanarkshire won a Pride of Britain Award last month and met the Prime Minister's wife Samantha Cameron at Downing Street.

Her family have claimed doctors "missed a big opportunity" to notice Ms Cafferkey had become unwell again.

They said it "absolutely diabolical" a GP in Glasgow had sent her home after she went to an out-of-hours clinic.

But the authorities insisted appropriate action had been taken.

Some 58 close contacts of the nurse have been identified, with 40 of those offered vaccinations as a precaution.

Dr Derek Gatherer, from Lancaster University, has previously told Sky News that people who fight off Ebola produce antibodies that "kill off the virus in most bodily fluids".

But he added: "In areas of the body where the immune system is not particularly active - one of these is the central nervous system ... the Ebola virus can survive in very small quantities."

A Save The Children report found Ms Cafferkey was probably originally infected because she had used a visor to protect her face after struggling to get her goggles to fit.