title: Etiology and clinical characteristics of influenza-like illness (ILI) in outpatients in Beijing, June 2010 to May 2011.
abstract: BACKGROUND
  Since May 2009, exposure of the population of Beijing, China to pH1N1 has resulted in an increase in respiratory illnesses. Limited information is available on the etiology and clinical characteristics of the influenza-like illness (ILI) that ensued in adults following the pH1N1 pandemic.
  
  
  METHODS
  Clinical and epidemiological data of ILI in adults was collected. A total of 279 throat swabs were tested for twelve respiratory viruses using multiplex RT-PCR. Clinical characteristics of influenza A in outpatients versus test-negative patients were compared using Pearson's χ2 and the Mann-Whitney U test. 190 swabs were tested for pH1N1 by virus isolation. Consultation rates for ILI were compared between 2009 and 2010.
  
  
  RESULTS
  One or two virus were detected in 29% of the samples. Influenza A virus (FLU-A) accounted for 22.9% (64/279). Other viruses were present at a frequency less than 3.0%. Cough was significantly associated with Influenza A virus infection (χ2, p<0.001). The positive rate of FLU-A was consistent with changes in the ILI rate during the same period and there was a significant reduction in the incidence of ILI in 2010 when compared to 2009. During the 2010-2011 influenza season, the incidence peaked in January 2011 in Beijing and north China.
  
  
  CONCLUSIONS
  Exposure to pH1N1 had no impact on typical influenza seasonal peaks, although FLU-A remained the predominant virus for 2010 in Beijing. Symptomatically, cough was associated with FLU-A infection. The positive rate of influenza virus was consistent with changes in the ILI rate during the same period and there was a significant reduction in the incidence of ILI in 2010 when compared to that of 2009.
authors.affiliation: Department of Infectious Disease, Peking University Hepatology Institute, Peking University People's Hospital, Beijing, China.
authors.forename: XiaoHua
authors.initials: X
authors.lastname: Yang
authors.forename: Yao
authors.initials: Y
authors.lastname: Yao
authors.forename: MeiFang
authors.initials: M
authors.lastname: Chen
authors.forename: Xia
authors.initials: X
authors.lastname: Yang
authors.forename: YanDi
authors.initials: Y
authors.lastname: Xie
authors.forename: YaFen
authors.initials: Y
authors.lastname: Liu
authors.forename: XiuYing
authors.initials: X
authors.lastname: Zhao
authors.forename: Yan
authors.initials: Y
authors.lastname: Gao
authors.forename: Lai
authors.initials: L
authors.lastname: Wei
mesh_terms: D000328:Adult; D002681:China / Q000453:epidemiology; D005260:Female; D006801:Humans; D007251:Influenza, Human / Q000097:blood / Q000453:epidemiology* / Q000209:etiology* / Q000821:virology*; D008297:Male; D008875:Middle Aged; D009975:Orthomyxoviridae / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D010045:Outpatients / Q000706:statistics & numerical data; D010641:Phenotype; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012621:Seasons; D012703:Serotyping; D013997:Time Factors; D055815:Young Adult