Case-control study of risk factors for human infection with influenza A(H7N9) virus in Jiangsu Province, China, 2013

We describe a case-control study performed in Jiangsu, China, to evaluate risk factors for human infection with novel avian influenza A(H7N9) virus. Twenty-five cases and 93 controls matched by age, sex, and location were included in the study. Direct contact with poultry or birds in the two weeks before illness onset, chronic medical conditions (hypertension excluded), and environment-related exposures were significantly associated with A(H7N9) infection. Since it was discovered in February 2013, the emerging outbreak of human infections with a novel avian influenza A(H7N9) virus in China, has raised serious concerns for public health throughout the world [1]. According to reports by China National Health and Family Planning Commission, a total of 130 confirmed cases of human infection including 37 deaths (28%) were reported in mainland China as of 27 May 2013. Few descriptive studies have been reported on risk factors associated with avian influenza A(H7N9) virus infection [1,2]. We conducted a matched case-control study to identify potential risk factors for human influenza A(H7N9) cases in Jiangsu Province, one of the areas where the novel reassortant influenza A(H7N9) virus emerged earliest.