title: An epidemiological study of 1348 cases of pandemic H1N1 influenza admitted to Singapore Hospitals from July to September 2009.
abstract: BACKGROUND
  We reviewed the epidemiological features of 1348 hospitalised cases of influenza A (H1N1-2009) [pandemic H1N1] infection in Singapore reported between 15 July and 28 September 2009.
  
  
  METHODS
  Data on the demographic and epidemiological characteristics of hospitalised patients with confirmed pandemic H1N1 infection were collected from all restructured and private hospitals in Singapore using a standard template and were analysed retrospectively.
  
  
  RESULTS
  Of the 1348 cases, 92 were classified as severely ill (i.e. were admitted to an intensive care unit and/or who died). Of these severely ill cases, 50 (54.3%) required mechanical ventilation. While overall hospitalisation rates were highest in the 0 to 11 months age group, the incidence of severely ill cases was highest in patients aged 65 years and older. Fifty per cent of all hospitalised cases and 28% of all severely ill cases did not have any underlying medical conditions. The following factors were found to be independently associated with a higher likelihood of severe illness: older age and the presence of the following comorbidities: neuromuscular disorders, epilepsy and obesity.
  
  
  CONCLUSIONS
  Between 15 July and 28 September 2009, pandemic H1N1 infection caused significant illness requiring hospitalisation, as well as intensive care and mechanical ventilation in some cases. There were 18 deaths from pandemic H1N1 during this period, which corresponded to a case-fatality rate of 7 deaths for every 100,000 cases of pandemic H1N1.
authors.affiliation: Communicable Diseases Division, Ministry of Health, Singapore. hariharan_subramony@moh.gov.sg
authors.forename: Hariharan
authors.initials: H
authors.lastname: Subramony
authors.forename: Florence Y L
authors.initials: FY
authors.lastname: Lai
authors.forename: Li Wei
authors.initials: LW
authors.lastname: Ang
authors.forename: Jeffery L
authors.initials: JL
authors.lastname: Cutter
authors.forename: Poh Lian
authors.initials: PL
authors.lastname: Lim
authors.forename: Lyn
authors.initials: L
authors.lastname: James
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks; D016021:Epidemiologic Studies; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data / Q000639:trends; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D053118:Influenza A Virus, H1N1 Subtype / Q000302:isolation & purification*; D007251:Influenza, Human / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D012121:Respiration, Artificial / Q000706:statistics & numerical data; D012189:Retrospective Studies; D012720:Severity of Illness Index; D012846:Singapore / Q000453:epidemiology; D055815:Young Adult