Abstract: ObjectiveTo estimate the excess numbers of influenza-associated influenza-like illness (ILI) cases in Guangzhou City during 2011 to 2016.MethodsILI and influenza reported cases data were obtained from “Public health emergency surveillance and early warning system” and “Infectious disease report information management system”. The correlation between the ILI and influenza cases were analyzed. The excess numbers of influenza-associated ILI cases were estimated by Serfling regression model.ResultsA total of 57 642 influenza cases and 2 242 332 ILI cases were reported by 19 sentinel hospitalsduring 2011 to 2016. A positive correlation was observed between ILI and influenza cases(r=0.57, P<0.01). In the Serflingreg ression model, there were 84 epidemic weeks in 282 weeks, and 322 509 (95%CI: 204 346~440 672) excess influenza-associated ILI cases were estimated. The excess numbers of influenza-associated ILI cases were 37 197 (95%CI: 14 547 - 59 846), 52 432 (95%CI: 29 980 -74 885), 21 846 (95%CI: 9 244 - 34 448), 74 880 (95%CI: 46 867 - 102 893), 75 138 (95%CI: 59 705 - 90 570), and 61 016 (95%CI: 44 003 - 78 030) in each year,accounting for 10.88% (95%CI: 4.26% - 17.51%), 13.31% (95%CI: 7.61% - 19.01%), 5.87% (95%CI: 2.49% - 9.26%), 17.35% (95%CI: 10.86% - 23.84%), 16.56% (95%CI: 13.16% - 19.96%), 24.47% (95%CI: 17.65% - 31.30%) of all ILI cases over the same period of different years, respectively. The excess rates were 13.23% and 19.63% in groups aged <15 years and aged ≥15 years, respectively.ConclusionInfluenza epidemics can cause tens of thousands of excess ILI cases every year in Guangzhou City during 2011-2016.The excess rate was higher in people aged ≥15 years, which can lead to a heavy disease burden.