Avian influenza A (H7N9) virus infections in humans across five epidemics in mainland China, 2013–2017

Human infections due to a novel avian influenza A (H7N9) virus were first confirmed in Mar 2013 in China in three urban residents hospitalized with severe pneumonia in Shanghai and Anhui (1). The incubation period of human infection with the A (H7N9) virus ranges from 1 to 10 days, with an average of 5 days. The median duration from exposure to poultry to onset of illness was 6 days, while the median duration from illness onset to hospitalization, progression to acute respiratory distress syndrome (ARDS), commencement of antiviral therapy, and death were 4, 7, 6, and 21 days respectively (2).