Another person in the UK has been diagnosed with the deadly Sars-like virus after catching the disease from a family member.
The patient becomes the third person in a week to contract the disease.
The Health Protection Agency (HPA) said on Monday that a person who had been travelling in the Middle East had been hospitalised in Manchester with the coronavirus.
The HPA has announced that another member of the same family has caught the disease and was being treated in isolation. The patient was said to be recovering.
Four out of the 12 confirmed global coronavirus cases have been diagnosed in Britain.
Prof John Watson, head of the respiratory diseases department of the HPA, said: "Although this 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 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.
Preventing spread of infection
"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."
Of the 12 confirmed cases, five people have died - three in Saudi Arabia and two in Jordan. Another case was confirmed in Germany, where the patient recovered.
Coronaviruses cause of the common cold but can result in more severe illnesses including Sars (severe acute respiratory syndrome).
The latest outbreak was first identified in September, three months after the first fatality.
Those infected develop serious respiratory illnesses coupled with a fever, cough, shortness of breath, and breathing difficulties.