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.