关键词: 流感, 人；发病率；变化趋势；轨迹模型

Abstract: Background　Influenza is a common acute respiratory disease with a high incidence，which often affects the quality of life，and may result in serious complications and may even lead to death.So monitoring and analyzing influenza are essential for the prevention and control of this disease.Objective　To explore the incidence and trend of influenza in China from 2005 to 2015 by region，sex and age group，and to determine the developmental trajectory of subgroups.Methods　The research was developmented from February to November 2018.The data of incidence of influenza in China from 2005 to 2015 were obtained from the National Scientific Data Sharing Platform for Population and Health.Descriptive analysis was performed on the incidence of influenza by region，sex and age group，and annual growth rate during the period was calculated.The trajectory model was used to explore the number of subgroups and corresponding characteristics of different trajectories.Results　During this period，the annual incidence of influenza increased from 3.51% in 2005 to 14.37% in 2015，generally showing an upward trend.Males had a higher overall incidence than females.But the average annual growth rate was higher in females（15.93%） than that in males（14.51%）.And greater increase of incidence was found in the elderly aged 70-year-old and above（32.04%） and children below 5 years old（29.41%）.Three types of trajectories could be categorized for different trends of influenza.The first subgroup had the highest incidence with a general upward trend，gradually reaching a relatively steady state，in particular，the situation of prevention and control for people under 5 years old and 5-14 years old in Tianjin，Hebei，Shanghai，Fujian，Hubei，Hunan，Guangdong，Gansu and Ningxia is more severe.The second subgroup had a mid-level incidence and a continual increase，it is urgent to control its rising momentum. Shanxi and Henan are the areas that need to be focused on. The lowest incidence was found in the third subgroup，which increased slowly.Conclusion　The incidence of influenza in China from 2005 to 2015 had different trajectories.Identifying different trajectories of age-，gender-，and region-specific incidence of influenza is helpful for taking targeted measures for influenza prevention and control.

Key words: Influenza, human；Incidence；Change trend；Trajectory model