A second relative of a UK patient who recently contracted a potentially fatal Sars-like virus has become infected with the disease, taking the total to three within the family, health experts said.
On Monday, the Health Protection Agency (HPA) said one person who had recently travelled to the Middle East and Pakistan was being treated in an intensive care unit at a Manchester hospital after becoming infected with a new type of coronavirus.
On Wednesday, a relative of the patient who had no recent travel history became infected and now the HPA has said a third person, who has also not travelled recently, is infected.
But the HPA said the risk associated with novel coronavirus to the UK population remained low.
The newest patient is recovering from a mild respiratory illness and is currently well. This latest case brings the total number of confirmed cases globally to 12, of which four have been diagnosed in the UK.
The second family member has an existing medical condition that might have made them more susceptible to respiratory infections, the HPA said on Wednesday.
Professor John Watson, head of the respiratory diseases department at the HPA, said: "Although this (third) patient had a mild form of respiratory illness, as a precaution the HPA is advising that the patient self-isolate and limit contact with non-household members. Follow up of other household members and contacts of this case is currently under way.
"Although this case appears to be due to person-to-person transmission, the risk of infection in contacts in most circumstances is still considered to be low.
"If novel coronavirus were more infectious, we would have expected to have seen a larger number of cases than we have seen since the first case was reported three months ago.
"However, this new development does justify the measures that were immediately put into place to prevent any further spread of infection and to identify and follow up contacts of known cases.
"We would like to emphasise that the risk associated with novel coronavirus to the general UK population remains very low.
"The HPA will continue to work closely with national and international health authorities and will share any further advice with health professionals and the public if and when more information becomes available."
Last year British health officials identified another case of the novel coronavirus.
A 49-year-old Qatari man was treated at St Thomas' Hospital in London after becoming infected.
Five patients have died as a result of the infectious disease, none in the UK.
The HPA said there have been five cases confirmed in Saudi Arabia resulting in three deaths, while two patients treated in Jordan both died.
A patient from Qatar was treated in Germany but has since been discharged.
Infected patients have presented with serious respiratory illness with fever, cough, shortness of breath and breathing difficulties.
Coronaviruses cause most common colds but can also cause Sars (severe acute respiratory syndrome). In 2003, hundreds of people died after a Sars outbreak in Asia.Suggest a correction