[Burden of influenza-associated consultations in China from 2011 to 2021 surveillance years]

Abstract

Objective: To estimate the burden of influenza-associated outpatient consultations in China from 2011 to 2021 surveillance years to provide a reference for developing influenza prevention, control strategies, and vaccination policies. Methods: Data on influenza-like illness (ILI) and virological confirmation of sentinel specimens from 2011 to 2021 surveillance years were extracted from China's national sentinel surveillance system. Generalized additive models were fitted to estimate influenza-associated excess ILI outpatient burden, accounting for seasonal baselines and meteorological factors. Results: Influenza was associated with an average of 1.66 (95%CI: 1.51-1.80) excess ILI consultations per 1 000 person-years (py) in China each year from 2011 to 2021 surveillance years. The influenza-associated outpatient burden was similar across different virus types/subtypes. Influenza A(H1N1)pdm09 led to a higher rate of influenza- associated ILI consultations [0.65 (95%CI: 0.53-0.76) per 1 000 py] compared to other types/subtypes. The age groups with the highest burdens were children aged 0-4 years and 5-14 years, with excess outpatient consultation rates of 15.23 (95%CI: 13.73-16.73) per 1 000 py and 13.53 (95%CI: 12.49-14.52) per 1 000 py, respectively. Conclusions: Influenza caused many outpatient consultations in China, particularly among children aged 0-14. Continuous influenza monitoring and disease burden assessment should be conducted, and close attention should be paid to the changing trends of various influenza virus types/subtypes. When formulating vaccination strategies, priority should be given to recommending vaccination for high-risk populations, such as children.