There may have been limited human-to-human transmission of a new coronavirus in China within families, and it is possible there could be a wider outbreak, the World Health Organization (WHO) said on Tuesday. Coronaviruses are a large family of viruses that can cause infections ranging from the common cold to Sars. A Chinese woman has been quarantined in Thailand with a mystery strain of coronavirus, Thai authorities said on Monday, the first time the virus has been detected outside China.

In all, 41 cases of pneumonia have been reported in the central Chinese city of Wuhan, which preliminary lab tests cited by state media showed could be from a new type of coronavirus. One of the patients has died.

"From the information that we have it is possible that there is limited human-to-human transmission, potentially among families, but it is very clear right now that we have no sustained human-to-human transmission," said Maria Van Kerkhove, acting head of WHO's emerging diseases unit.

The WHO is however preparing for the possibility that there could be a wider outbreak, she told a Geneva news briefing. "It is still early days, we don't have a clear clinical picture." Some types of the virus cause less serious diseases, while others - like the one that causes MERS - are far more severe.