Epidemiological characteristics and outbreak management of influenza in Yunnan province, 2010 – 2021

  Objective  To analyze epidemiological characteristics and outbreak management of influenza in Yunnan province and to provide evidence for developing effective prevention and control strategies.

  Methods  The data on reported influenza cases and outbreaks in Yunnan province during 2010 – 2021 were collected from China Information System for Disease Control and Prevention and analyzed using descriptive statistics.

  Results  Totally 85 018 influenza cases and 13 deaths were reported in the province during the 12-year period, with the average annual incidence of 14.9895/100 000. Although the cases were reported in populations of various ages, the majority (52.64%) of the cases were at ages of 0 – 9 years and only 7.18% of the cases were elderly people aged ≥ 60 years. The top three average annual influenza incidence (82.7681, 37.9560, and 34.1800 per 100 000 population) were observed in three prefectures, namely Dehong, Honghe and Diqing. There were altogether 16 000 reported cases with laboratory confirmation, of them, 50.99% and 48.14% had influenza A and B virus infection, and 0.87% had combined infection of influenza A and B. Among 127 influenza outbreaks identified during the period in the province, 120 occurred in schools; 64 and 54 caused by influenza B and A virus infection, and 9 were induced by combined infection of influenza A and B virus. For the outbreaks, the average total number of reported cases in one outbreak was 69.6; the interval between the report of first case and the identification of the outbreak ranged 4.5 – 10 days; and the median duration of the outbreaks was 12 days (25th, 75th percentile: 8, 19). The interval between the report of first case and the identification of an outbreak was positively correlated with the duration of the outbreak (r_S = 0.518, P < 0.05).

  Conclusion  During 2010 – 2021 in Yunnan province, influenza was prevalent from November of a year to January of the next year, especially among children aged 0 – 9 years and the most of the influenza outbreaks occurred in schools, suggesting that influenza vaccination should be promoted among high-risk populations to control the epidemic in the province.