A British nurse who contracted Ebola while working in Sierra Leone last year has been readmitted to hospital with an "unusual late complication" from the infection.

Pauline Cafferkey was transferred from the Queen Elizabeth University Hospital in Glasgow to the Royal Free London hospital this morning in a military aircraft under supervision.

In a statement, the Royal Free said she is in a serious condition.

"She will now be treated in isolation in the hospital's high-level isolation unit under nationally agreed guidelines," the statement read.

"The Ebola virus can only be transmitted by direct contact with the blood or bodily fluids of an infected person while they are symptomatic so the risk to the general public remains low and the NHS has well established and practised infection control procedures in place."

Professor Paul Cosford, medical director at Public Health England, said the Scottish health authorities will be following up on a number of close contacts of Ms Cafferkey's as a precaution.

The nurse is believed to have carried out vaccinations on children in the last couple of months.

One viewer wrote to Sky News saying she was a "very competent nurse, done my boys jabs, lovely lassie, hope she's ok. Still scares you a wee bit though".

Another Sky News viewer said: "She did my daughters jabs too, only a couple of months back."

The nurse was first diagnosed with Ebola in December last year and spent almost a month in isolation at the Royal Free before being discharged in January.

She was treated with an experimental anti-viral drug and blood taken from survivors of the disease.

However, Professor John Edmunds, from the London School of Hygiene and Tropical Medicine, said the Ebola virus can occasionally persist for some months in certain tissues within survivors.

"The risk of transmission from these individuals appears to be very low," he said.

"However, with so many survivors in West Africa now, there is a risk that further outbreaks can be triggered, which is why authorities have to remain very vigilant."

Ms Cafferkey won a Pride of Britain award last month and met the Prime Minister's wife Samantha Cameron at Downing Street along with other winners.

Her complications come after the three West African countries at the centre of the Ebola epidemic recorded their first week with no new cases since the outbreak was declared in March 2014.

More than 11,000 people have died in Guinea, Liberia and Sierra Leone, according to figures from the World Health Organisation (WHO).