The first cases of human infection with the avian influenza A(H7N9) virus were identified in China in early 2013. This report describes findings for 139 persons with confirmed H7N9 virus infection through December 1, 2013. The first identified cases of human infection with a novel influenza A(H7N9) virus occurred in eastern China during February and March 2013 and were characterized by rapidly progressive pneumonia, respiratory failure, the acute respiratory distress syndrome (ARDS), and fatal outcomes. 1 We analyzed available data from field investigations to characterize the descriptive epidemiology of laboratory-confirmed cases of avian influenza A(H7N9) virus infection in humans that were reported to the Chinese Center for Disease Control and Prevention (China CDC) as of December 1, 2013. In this report, we summarize the epidemiologic findings of case investigations and follow-up monitoring of close contacts of . . .