title: [Estimation on the real number of novel influenza A (H1N1) cases, Beijing, 2009].
abstract: OBJECTIVE
  To estimate the real number of novel influenza A (H1N1) infection in Beijing, 2009.
  
  
  METHODS
  A multiplier model (Impact 2009 v 1.0 software) based on Monte Carlo approach was used to estimate the real number of novel influenza A (H1N1) based on the number of influenza-like illness (ILI) cases, novel influenza A (H1N1) positive rate among ILI cases and rate on clinical visit of ILIs in secondary and tertiary hospitals.
  
  
  RESULTS
  There were 1.80 million (90%CI: 1.46 - 2.30) estimated novel influenza A (H1N1) cases in 2009 in Beijing with the rate of infection as 11.0%. One reported case would represent 167 real infections. The highest age groups of infection were 0 - 4 years and 5 - 14 years, being 32.5% and 33.3%, respectively.
  
  
  CONCLUSIONS
  Laboratory-confirmed infections with novel influenza A (H1N1) only represented a fraction of the total cases in a population, suggesting that it was imperative to estimate the real number of novel influenza A (H1N1) infection.
authors.affiliation: Beijing Center for Disease Control and Prevention, Beijing 100013, China.
authors.forename: Xiao-li
authors.initials: XL
authors.lastname: Wang
authors.forename: Peng
authors.initials: P
authors.lastname: Yang
authors.forename: Xiang-feng
authors.initials: XF
authors.lastname: Dou
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
authors.forename: Wen-ting
authors.initials: WT
authors.lastname: Liu
authors.forename: Ying
authors.initials: Y
authors.lastname: Deng
authors.forename: Xing-huo
authors.initials: XH
authors.lastname: Pang
authors.forename: Xiong
authors.initials: X
authors.lastname: He
authors.forename: Quan-yi
authors.initials: QY
authors.lastname: Wang
mesh_terms: D000293:Adolescent; D000328:Adult; D000465:Algorithms; D002648:Child; D002675:Child, Preschool; D002681:China / Q000453:epidemiology; D058872:Epidemics; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D053118:Influenza A Virus, H1N1 Subtype; D007251:Influenza, Human / Q000453:epidemiology* / Q000517:prevention & control / Q000821:virology; D008297:Male; D008875:Middle Aged; D018571:Sentinel Surveillance; D055815:Young Adult