Abstract：Objective To investigate the regularity of influenza epidemics in Hunan Province during 2007-2016, and to provide a scientific basis for prevention and control of influenza in future. Methods Descriptive epidemiological methods were used to analyze the data concerning influenza like illness (ILI) cases, types/subtyps of influenza virus strains and influenza outbreaks reported in Hunan Province during 2007-2016. Results A total of 1,520,652 ILI cases were reported by sentinel hospitals during 2007-2016, accounting for 4.82% of the total outpatients from all the sentinel clinics. The number of ILI patients in the age groups of 0-, 5-, 15-, 25- and 60- years respectively accounted for 65.98%, 20.77%, 4.49%, 6.68% and 2.08% of the total ILI cases. Influenza epidemics peaked annually during the winter-spring and summer months in Hunan Province. A total of 8,788 (5.99%) influenza virus strains were isolated, including 476 strains of seasonal A(H1N1), 2,422 strains of A(H1N1) pdm09, 2,985 strains of H3N2, 1,361 strains of subtype B of Yamagata (BY), 1,532 strains of subtype B of Victorian (BV) and 12 strains of unknown type. The predominant strain changed every 1-2 years, and appeared alternately. A total of 264 ILI outbreaks were reported, and 230 occurred in primary and secondary schools, accounting for 87.12% of the total outbreaks. Conclusions There are two peaks of influenza epidemic each year in Hunan Province, one in winter-spring and a second in summer. H3, A(H1N1)pdm09 and type B strains are alternately dominant in an interval of 1-2 years. Prevention and control of influenza outbreaks should be focused on primary and secondary schools.
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