An outbreak of coronavirus in China is spreading to more cities, Chinese authorities reported on Monday, with 139 new cases found over the weekend, including a third death.

Shanghai: China reported Monday a sharp rise in the number of people infected with a new coronavirus, including the first cases in the capital. The outbreak coincides with the country's busiest travel period, as millions of board trains and planes for the Lunar New Year holidays.

Health authorities in the central city of Wuhan, where viral pneumonia appears to have originated, said an additional 136 cases have been confirmed in the city, which now has a total of 198 infected patients. As of the weekend, a third patient had died, bringing the death toll to three.

Two individuals in Beijing and one in the southern city of Shenzhen have also been diagnosed with the novel coronavirus, health commissions in the respective cities said Monday. The three people had visited Wuhan.

The outbreak has put other countries on alert as millions of Chinese travel for Lunar New Year. Authorities in Thailand and in Japan have already identified at least three cases, all involving recent travel from China.

At least a half-dozen countries in Asia and three US airports have started screening incoming airline passengers from central China.

Many of the initial cases had connections to a seafood market in Wuhan, which was closed for an investigation. As hundreds of people who came into close contact with diagnosed patients have not infected themselves, the municipal health commission maintains that the virus is not easily transmitted between humans, though it has not ruled out a limited human-to-human transmission.

China's National Health Commission said experts have judged the current outbreak to be “preventable and controllable.”

“However, the source of the new type of coronavirus has not been found, we do not fully understand how the virus is transmitted, and changes in the virus still need to be closely monitored,” the commission said in a Sunday statement.

Coronaviruses cause diseases ranging from the common cold to SARS, or severe acute respiratory syndrome. SARS first infected people in southern China in late 2002 and spread to more than two dozen countries, killing nearly 800.

The virus causing the current outbreak is different from those previously identified, Chinese scientists said earlier this month. Initial symptoms of the novel coronavirus include fever, cough, tightness of the chest and shortness of breath.

On the Weibo social media platform, which is widely used in China, people posted prevention advice such as wearing masks and washing hands. State broadcaster CCTV recommended staying warm, increasing physical activity, eating lightly and avoiding crowded places.