The Archbishop of Canterbury has urged Christians to pray for the Glasgow nurse diagnosed with Ebola after working with victims in Sierra Leone.

In a tweet posted yesterday, the Archbishop Justin Welby showed his appreciation for those working to combat the virus, writing: "we owe them thanks and respect", and asked for continued prayers.

Welby was tested for Ebola last week after having visited Sierra Leone earlier this month and missing his Christmas sermon due to illness, but was later diagnosed with pneumonia. In an earlier tweet he said he is recovering well, and branded the NHS "brill".

The Glasgow health worker, who had been working with Save the Children at an Ebola treatment centre in Sierra Leone, was this morning moved to London for treatment.

The woman arrived at the capital's Royal Free hospital, Britain's designated Ebola treatment centre, in an ambulance accompanied by several police vehicles, a Reuters witness said.

"We think so far certainly the clinical care for her is going as expected," said Paul Cosford, Director for Health Protection at Public Health England, the government body handling Britain's response to Ebola, on BBC radio.

"The agreement we have across the country is that the right place for treatment for people with Ebola is at the Royal Free in their specialist facilities... it's a clinical decision."

The World Health Organization said on Monday that the number of people infected by Ebola in the three West African countries worst affected by the outbreak - Sierra Leone, Liberia and Guinea - had passed 20,000, with more than 7,842 deaths so far.

The National Health Service worker, who had been working in West Africa with the charity Save the Children, flew from Sierra Leone to Glasgow late on Sunday on a British Airways flight via Casablanca in Morocco and London's Heathrow.

She was diagnosed with the deadly virus on Monday and was initially treated at Scotland's Gartnavel Hospital.

Scottish authorities have said the illness was diagnosed at an early stage, meaning the risk to others was considered extremely low, but they were investigating all possible contacts with the patient.

Earlier this year the Royal Free hospital successfully treated another British aid worker, William Pooley, who was flown home for treatment after being diagnosed with the virus in Sierra Leone.

Scottish First Minister Nicola Sturgeon said a second patient in Scotland was being tested for the virus after returning from West Africa, but had a low probability of having the virus, having had no known contact with infected people.

A third person was undergoing tests for the Ebola in Cornwall, England and was being treated in an isolation unit, a statement from Public Health England said. The results of that test would take at least 24 hours, the statement said.

(Additional reporting by Reuters)