BEIJING - China's health authority said humans are at a very low risk for contracting the lesser-known H7N9 bird flu, according to a Tuesday report in the Beijing News.

Only a few cases of human infections were reported in limited areas, and no additional infections have been found among those who came into contact with the H7N9 patients, the daily newspaper said, citing officials with the Chinese Center for Disease Control and Prevention (CCDCP).

The first known human deaths from the disease were two men in Shanghai, while a woman in nearby Anhui Province was also infected with the flu strain and is in critical condition, the National Health and Family Planning Commission (NHFPC) said Sunday.

It was not clear how the patients were infected, but there was no evidence of human-to-human transmission, the CCDCP said in a statement on its website.

The virulence and transmission capacity of the H7N9 can not be determined due to limited clinical cases and research data on the virus, the CCDCP added in the statement.

The symptoms of the three confirmed cases included typical viral pneumonia, with fever, coughing and other respiratory ailments at the onset. Patients had difficulty breathing after five to seven days, and the two men died of acute respiratory distress syndrome, according to the statement.

The NHFPC has sent several work groups to Shanghai Municipality and Anhui and Jiangsu provinces to determine the infection source of the flu strain and prevent the disease from spreading.