Seven human cases of H7N9 avian influenza — including two fatal cases — have been reported in the eastern part of the China around Shanghai. This is a different strain of bird flu from H5N1 avian influenza, which has killed 371 people out of 622 infected in 15 countries since 2003.

The four newest cases have been reported in China's eastern Jiangsu Province, including a woman in Nanjing who works slaughtering poultry, a man in Suzhou, a woman in Wuxi and a woman in Suqian. The official Chinese news agency Xinhua says 167 people who were in close contact with the four don't appear to have any flu symptoms.

A total of 167 people who had come into contact with the four showed no symptoms of fever or respiratory illnesses, it said. That suggests — but doesn't prove — that the virus isn't passing from person to person, said experts.

On March 31, China reported three H7N9 bird flu infections: two in Shanghai and one in Anhui. The two Shanghai victims died and the third patient is in critical condition, said Xinhua. There's no suggestion yet that they infected any of their friends or relatives, either, Chinese officials have said.

Chinese officials have not said what they are doing to see if the H7N9 virus is spreading among poultry flocks.