A new respiratory virus has been detected in a severely-ill patient from the Middle East who is being treated in a British hospital.
The Health Protection Agency (HPA) said the virus, which is associated with a new type of coronavirus, is the second confirmed case after a patient with acute respiratory illness in Saudi Arabia died from it in recent months.
The UK case involves a 49-year-old who had recently travelled to Saudi Arabia. The patient is in intensive care in a London hospital.
"In the light of the severity of the illness that has been identified in the two confirmed cases, immediate steps have been taken to ensure that people who have been in contact with the UK case have not been infected, and there is no evidence to suggest that they have," Professor John Watson, head of the respiratory diseases department at the HPA, said.
"Further information about these cases is being developed for healthcare workers in the UK, as well as advice to help maintain increased vigilance for this virus.
"This information is also being shared with national and international authorities including the World Health Organisation and the European Centre for Disease Control."
Watson said there was no specific evidence of ongoing transmission and he had no advice for the public or returning travellers.
The HPA said coronaviruses are causes of the common cold but can also include more severe illness, such as the virus responsible for Sars (Severe Acute Respiratory Syndrome).
This new virus, however, is different from any that have previously been identified in humans.
The HPA said it was aware of a small number of other cases of serious respiratory illness in the Middle East in the past three months including the person who died.
That person's illness is also being investigated but health authorities said there is no evidence at the moment to suggest that it is caused by the same virus or linked to the other two cases.