title: [Etiological characteristics of influenza A (H1N1) 2009 virus in Beijing].
abstract: OBJECTIVE
  To analyze the results of detection on influenza A (H1N1) 2009 virus in Beijing from May 2009 to December 2009 and to understand the epidemiologic characteristics during the pandemic period.
  
  
  METHODS
  The study was conducted from the May 1 to December 27, 2009. A total of 101 852 throat swab samples were detected with the real-time RT-PCR assay by the Beijing Network Laboratory. Data was statistically analyzed.
  
  
  RESULTS
  9843 samples showed influenza A (H1N1) 2009 positive, with an overall positive rate as 9.66%. In terms of the positive rates, they were 2.85% from May to June, 3.32% from July to August and 8.35% from September to October. The peak month fell in November (29.67%) and December (24.33%). The positive rates among the following subpopulations were: 8.40% among the suspected cases, 4.75% among close contact cases, 11.46% among the influenza-like illness cases and 7.33% among the cluster cases with fever. Positive cases mainly fell in age groups 5 - 14 and 15 - 24. The ratio of male to female was 1.5:1.
  
  
  CONCLUSIONS
  During the pandemic period of influenza A (H1N1) 2009, positive cases gradually increased during May to November but slowly decreasing in December.
authors.affiliation: Beijing Center for Disease Control and Prevention, Beijing 100013, China.
authors.forename: Fang
authors.initials: F
authors.lastname: Huang
authors.forename: Jing
authors.initials: J
authors.lastname: Guo
authors.forename: Shu-juan
authors.initials: SJ
authors.lastname: Cui
authors.forename: Yan-ning
authors.initials: YN
authors.lastname: Lü
authors.forename: Zhi-yong
authors.initials: ZY
authors.lastname: Gao
authors.forename: Wei-hong
authors.initials: WH
authors.lastname: Li
authors.forename: Han-qiu
authors.initials: HQ
authors.lastname: Yan
authors.forename: Mei
authors.initials: M
authors.lastname: Qu
authors.forename: Wei-xian
authors.initials: WX
authors.lastname: Shi
authors.forename: Gui-lan
authors.initials: GL
authors.lastname: Lu
authors.forename: Xin
authors.initials: X
authors.lastname: Zhang
authors.forename: Dai-tao
authors.initials: DT
authors.lastname: Zhang
authors.forename: Li-li
authors.initials: LL
authors.lastname: Tian
authors.forename: Hai-kun
authors.initials: HK
authors.lastname: Qian
authors.forename: Peng
authors.initials: P
authors.lastname: Yang
authors.forename: Xing-huo
authors.initials: XH
authors.lastname: Pang
authors.forename: Quan-yi
authors.initials: QY
authors.lastname: Wang
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D002681:China / Q000453:epidemiology; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics / Q000302:isolation & purification*; D007251:Influenza, Human / Q000453:epidemiology / Q000517:prevention & control* / Q000821:virology*; D008297:Male; D008875:Middle Aged; D020133:Reverse Transcriptase Polymerase Chain Reaction; D055815:Young Adult