Epidemiological features and trends of influenza incidence in mainland China: A population-based surveillance study from 2005 to 2015

Objectives: To investigate epidemiological features and trends of influenza incidence with 1,173,640 cases in mainland China from 2005 to 2015. Methods: Incidence and mortality data for influenza from 2005 to 2015 were provided by the data-center of China public health science and covered a population of about 1.3 billion people from 31 provinces and regions in mainland China. Joinpoint regression and exploratory spatial data analyses were used to examine the incidence trends from 2005 to 2015. Results: The first upsurge in influenza cases occurred in 2009, and the highest incidence of influenza occurred in 2014 (15.9045 cases/100,000 people). The average incidence per year from 2009 to 2015 was threefold higher than that from 2005 to 2008 (10.5308 vs 3.4589 cases/100,000 people; incidence rate ratio = 3.0446). The joinpoint regression results showed that there was an increasing influenza incidence trend from 2005 to 2015 (annual change in percentage = 13.6%, 95%CI 2.2–26.3, p = 0.0236). The seasonal pattern analysis showed that influenza typically occurred in winter and spring during each monitoring year, peaking from November to March the next year. Conclusions: This study will help governments to make valuable decisions in allocating scarce resources and providing strategies to limit the spread of influenza. Keywords: Influenza, Epidemiology, Mainland China, Incidence, Seasonal pattern