A mysterious SARS-like virus has killed a third person and spread around China including to Beijing, fueling fears of a major outbreak as millions begin travelling for the Lunar New Year in humanity's biggest migration.

The new coronavirus strain, first discovered in the central city of Wuhan, has caused alarm because of its connection to Severe Acute Respiratory Syndrome (SARS), which killed nearly 650 people across mainland China and Hong Kong between 2002 and 2003.

Wuhan has 11 million inhabitants and serves as a major transport hub, including during the annual Lunar New Year holiday, which begins later this week and sees hundreds of millions of Chinese people, travel across the country to visit family.

No human-to-human transmission has been confirmed so far, but authorities have previously said the possibility "cannot be excluded".

A third person was confirmed to have died, and 136 new cases were found over the weekend in Wuhan, the local health commission said, taking the total number of people to have been diagnosed with the virus in China to 201.