BEIJING -- 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 board trains and planes for the Lunar New Year holidays.

Health authorities in the central city of Wuhan, where the 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.

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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 U.S. 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 were not infected themselves, the municipal health commission maintains that the virus is not easily transmitted between humans, though it has not ruled out limited human-to-human transmission.

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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.