Objective To understand the epidemiological characteristics of influenza in Hongkou district of Shanghai,and to provide evidence for disease prevention and control. Methods Data of cases with influenzalike illness(ILI)were collected and analyzed in Hongkou district of Shanghai from 2012 to 2013regarding the disease etiology and clustering features. Results The average percentage of cases with ILI was 0.46 in influenza sentinel surveillance hospitals during the study period,and majority of cases were young a...