Shanghai's health authority has confirmed a new human case of infection by the H7N9 strain of avian influenza, the Chinese news agency Xinhua said.

The man diagnosed with H7N9 bird flu is being treated in a hospital, Xinhua reported.

Shanghai has already reported one human case of H7N9 infection this month.

Shanghai is China's largest city by population, with more than 24 million residents.

Bird flu is most likely to strike in winter and spring and farmers have in recent years increased cleaning regimes, animal detention techniques and built roofs to cover hen pens, among other steps, to prevent the disease.