China's Health Ministry confirmed Tuesday a new A/H1N1 influenza case in central Hunan Province, bringing the total confirmed cases on the Chinese mainland to 12.

The patient is a 19-year-old male from Changsha, capital of Hunan. The provincial health department said he had been studying at an unidentified U.S. university.

The patient boarded Air China flight CA982 from New York at 4 a.m.(Beijing time) Thursday and arrived in Beijing at 6 p.m. (Beijing time).

On Friday, he took a taxi with his mother to the airport. They then boarded Air China flight CA1349 and arrived in Changsha at 1:40 p.m.

He developed a sore throat and cough Friday and was put under observation at the Changsha Center for Disease Control and Prevention (CCDCP) the following day. On Monday, his cough worsened and he was sent to the Public Health Treatment Center in Changsha, where he remained under quarantine.

CCDCP has located 56 Hunan residents who were on the CA1349 flight and urged health authorities of 23 regions to find the remaining 101 passengers.

The patient had close contact with 21 Hunan residents, including flight passengers and those he met after arrival in Hunan. Eighteen have been quarantined and three others are being sought.

The ministry noted that he was on the same plane with a 65-year-old man who had the fourth case of A/H1N1 reported in Beijing.

Beijing's transit authority plans to improve ventilation in public buses and subway trains, in the wake of the report that the city's fifth confirmed A/H1N1 flu patient, and the ninth on the mainland, had traveled by subway twice before he was quarantined.

The city began to disinfect all bus stations and public vehicles early this month.

Shanghai, which reported one confirmed case, has conducted onboard quarantine inspection on all incoming international flights.

Editor: Yan