Another person tested positive for the A/H1N1 influenza in Beijing, the capital's municipal health bureau said Wednesday.
This is the second confirmed case in Beijing and the fifth on China's mainland.
The patient is a 21-year-old Chinese-Canadian who studied at a college in Toronto, according to a health bureau publicity official who is surnamed Sun.
Sun refused to disclose the patient's name, saying he was no longer a Chinese national and his family hasn't agreed to do so.
The man arrived in Beijing in the afternoon of May 16 aboard a direct Air Canada flight from Toronto.
His parents picked him up from the airport and he remained at home for most of the time, Sun said.
The patient developed a fever and cough Tuesday morning and went to General Hospital of the Armed Police Forces at 6:30 p.m..
He was transferred to the Beijing Ditan Hospital Wednesday noon, where he tested positive for A/H1N1 flu and was quarantined.
China has previously reported four cases on the mainland -- in Sichuan, Shandong, Beijing and Guangdong, with the first two patients having been discharged.
The third patient, or the first confirmed in Beijing, was a 18-year-old woman surnamed Liu who had returned from the United States. She was confirmed to have the flu Saturday but described as in "stable condition".
The patient in Guangdong, surnamed Yang, is also recovering, said Yin Zhibiao, vice president with the No. 8 People's Hospital where he has been treated since Friday.
The doctor called for respect of patients' privacy.
"Yang asked me to do him a favor," he said. "He doesn't like media to pry into his personal information, which he believed had already brought forth some bad influence to his family."