A second relative of a UK patient who contracted a potentially fatal Sars-like virus has become infected with the disease, taking the total to three within the family.
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.
The second family member has an existing medical condition that might have made them more susceptible to respiratory infections, the HPA has said.
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."
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.
Infected patients have presented with serious respiratory illness with fever, cough, shortness of breath and breathing difficulties.