British nurse Pauline Cafferkey, who is being treated in a London hospital after contracting Ebola in Sierra Leone, could remain in a critical condition for "some time", her family has said.

Relatives said in a statement: "We would like to thank all our friends, family and the members of the public who have contacted us with support following Pauline's diagnosis with Ebola. We have been very touched by the kind words.

"Pauline continues to be in a critical condition at the Royal Free Hospital. We want to thank all the staff caring for her for their kindness, support and compassion. Pauline's condition could remain the same for some time and we would again ask for her and our privacy to be respected."

Ms Cafferkey was diagnosed with Ebola following her return to Glasgow from Sierra Leone where she had been a volunteer with Save the Children at the Ebola Treatment Centre in Kerry Town.

Officials from Public Health England and Health Protection Scotland are reviewing the UK's screening procedures for Ebola after it emerged Ms Cafferkey, 39, had been cleared to fly from London to Glasgow despite her temperature being checked seven times after she landed at Heathrow.

The nurse from Cambuslang was admitted to an isolation facility at Glasgow's Gartnavel Hospital on December 29.

After a blood sample tested positive for Ebola, she was transferred by military plane to the Royal Free Hospital the following day. Her condition deteriorated in the new year and remains critical.

Save the Children has launched an investigation into how she was infected but admits it may never establish the exact circumstances.

Health Secretary Jeremy Hunt said Ms Cafferkey "continues to receive the best possible care".

Ms Cafferkey's diagnosis has brought fresh scrutiny on the UK's preparedness for cases of Ebola, which can only be contracted by coming into contact with the bodily fluids of an infected person.

The nurse was allowed to travel on to Glasgow from London despite raising concerns about her health at Heathrow.

Previously, any possible Ebola carriers were advised to avoid crowded places and long journeys on public transport within the 21-day potential incubation period once they arrived back in the UK.

Mr Hunt said the guidance has since been strengthened to ensure anyone from a high-risk group who feels unwell is reassessed and advice will be sought immediately from an infectious diseases specialist.

He told the Commons on Monday that screening arrangements at Heathrow had been found to be working well and will be kept under review.

UK-based passengers on the flight Mrs Cafferkey was on from Casablanca, Morocco, to Heathrow and those on the flight from London to Glasgow have been contacted, he said.

Scotland's First Minister Nicola Sturgeon has hailed the ''quiet heroism'' of the nurse and others who "make all of us safer by placing themselves at risk".

She told MSPs: ''I hope there are no other cases identified in Scotland or the UK but it is likely we will see other cases, a small number of additional cases, and we need to keep learning from the experience of dealing with them.''