title: Epidemiological and Virological Characteristics of Influenza in Chongqing, China, 2011-2015.
abstract: BACKGROUND
  Chongqing is the largest municipality and located in Southwestern of China, with over 30 million registered inhabitants. There are few reports regarding the epidemiology of influenza in Chongqing. The objective of the paper is to explore the epidemiology of influenza in Chongqing, in order to provide scientific basis for prevention and control of influenza.
  From 2011 to 2015, we collected information on influenza-like illness (ILI) patients fulfilling the case definition, and took nasalpharyngeal or throat swabs specimens from ILI cases per week at the 7 sentinel hospitals. Specimens were tested by reverse transcription-polymerase chain reaction(RT-PCR) for influenza. Descriptive epidemiology was applied to analyze the epidemiology and etiology of influenza. A total of 9,696,212 cases were enrolled, of which 111,589 were ILI. Of those 24,868 samples from ILI cases, 13.3% (3,314/24,868) tested positive for influenza virus (65.7% influenza A, 34.1% influenza B, and 0.2% influenza A and B co-infection). Among the influenza A viruses, 71.3% were seasonal influenza A(H3N2) and 28.7% were influenza A(H1N1)pdm09. No cases of seasonal A(H1N1) were detected. The isolation rate was highest in children aged 5-14 years old. Influenza activity consistently peaked during January-March in 2011-2015, and June-July in 2012, 2014 and 2015.
  
  
  CONCLUSIONS
  Influenza is an important public health problem among ILI patients in Chongqing, especially among school-aged children. It might be beneficial to prioritize influenza vaccination for school-aged children and implement the school-based intervention to prevent and mitigating influenza outbreaks in Chongqing, particularly during the seasonal peaks.
authors.affiliation: Chongqing Municipal Center for Disease Control and Prevention, Chongqing, China.
authors.forename: Li
authors.initials: L
authors.lastname: Qi
authors.affiliation: Chongqing Municipal Center for Disease Control and Prevention, Chongqing, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Xiong
authors.affiliation: Chongqing Municipal Center for Disease Control and Prevention, Chongqing, China.
authors.forename: Bangzhong
authors.initials: B
authors.lastname: Xiao
authors.affiliation: Chongqing Municipal Center for Disease Control and Prevention, Chongqing, China.
authors.forename: Wenge
authors.initials: W
authors.lastname: Tang
authors.affiliation: Chongqing Municipal Center for Disease Control and Prevention, Chongqing, China.
authors.forename: Hua
authors.initials: H
authors.lastname: Ling
authors.affiliation: Chongqing Municipal Center for Disease Control and Prevention, Chongqing, China.
authors.forename: Jiang
authors.initials: J
authors.lastname: Long
authors.affiliation: Chongqing Municipal Center for Disease Control and Prevention, Chongqing, China.
authors.forename: Dayong
authors.initials: D
authors.lastname: Xiao
authors.affiliation: Chongqing Municipal Center for Disease Control and Prevention, Chongqing, China.
authors.forename: Han
authors.initials: H
authors.lastname: Zhao
authors.affiliation: Chongqing Municipal Center for Disease Control and Prevention, Chongqing, China.
authors.forename: Sheng
authors.initials: S
authors.lastname: Ye
authors.affiliation: Chongqing Municipal Center for Disease Control and Prevention, Chongqing, China.
authors.forename: Shuang
authors.initials: S
authors.lastname: Chen
authors.affiliation: Chongqing Municipal Center for Disease Control and Prevention, Chongqing, China.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Yu
authors.affiliation: Chongqing Municipal Center for Disease Control and Prevention, Chongqing, China.
authors.forename: Qin
authors.initials: Q
authors.lastname: Li
mesh_terms: D002681:China / Q000453:epidemiology; D006801:Humans; D007251:Influenza, Human / Q000453:epidemiology* / Q000821:virology; D011159:Population Surveillance