The avian influenza strain of H7N9 is highly likely to return and affect humans in the autumn and winter on the Chinese mainland, warned Zeng Guang, chief epidemiologist at the Chinese Center for Disease Control and Prevention.

China has remained free of new human H7N9 cases for more than a month since the last fatality - a 51-year-old woman who died of multiple organ failure caused by the virus on Aug 12 in Huizhou, Guangdong province - according to the National Health and Family Planning Commission.

The woman, who was transferred from Langfang, Hebei province, in mid July, worked in slaughtering poultry at a local market.