title: Lessons from the epidemiological surveillance program, during the influenza A (H1N1) virus epidemic, in a reference university hospital of Southeastern Brazil.
abstract: BACKGROUND
  The case definition of influenza-like illness (ILI) is a powerful epidemiological tool during influenza epidemics.
  
  
  METHODS
  A prospective cohort study was conducted to evaluate the impact of two definitions used as epidemiological tools, in adults and children, during the influenza A H1N1 epidemic. Patients were included if they had upper respiratory samples tested for influenza by real-time reverse transcriptase polymerase chain reaction during two periods, using the ILI definition (coughing + temperature ≤ 38ºC) in period 1, and the definition of severe acute respiratory infection (ARS) (coughing + temperature ≤ 38ºC and dyspnoea) in period 2.
  
  
  RESULTS
  The study included 366 adults and 147 children, covering 243 cases of ILI and 270 cases of ARS. Laboratory confirmed cases of influenza were higher in adults (50%) than in children (21.6%) ( p < 0.0001) and influenza infection was more prevalent in the ILI definition (53%) than ARS (24.4%) (p < 0.0001). Adults reported more chills and myalgia than children (p = 0.0001). Oseltamivir was administered in 58% and 46% of adults and children with influenza A H1N1, respectively. The influenza A H1N1 case fatality rate was 7% in adults and 8.3% in children. The mean time from onset of illness until antiviral administration was 4 days.
  
  
  CONCLUSIONS
  The modification of ILI to ARS definition resulted in less accuracy in influenza diagnosis and did not improve the appropriate time and use of antiviral medication.
authors.affiliation: Departamento de Clínica Médica, Faculdade de Ciências Médicas, Universidade Estadual de Campinas, Campinas, SP, Brazil. mlmoretti@hc.unicamp.br
authors.forename: Maria Luiza
authors.initials: ML
authors.lastname: Moretti
authors.forename: Verônica
authors.initials: V
authors.lastname: Sinkoc
authors.forename: Luis Gustavo de Oliveira
authors.initials: LG
authors.lastname: Cardoso
authors.forename: Gema Jesus de
authors.initials: GJ
authors.lastname: Camargo
authors.forename: Luis Felipe
authors.initials: LF
authors.lastname: Bachur
authors.forename: Christian Cruz
authors.initials: CC
authors.lastname: Hofling
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Angerami
authors.forename: Plínio
authors.initials: P
authors.lastname: Trabasso
authors.forename: Márcia Teixeira
authors.initials: MT
authors.lastname: Garcia
authors.forename: Mariângela Ribeiro
authors.initials: MR
authors.lastname: Resende
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D000368:Aged; D000998:Antiviral Agents / Q000627:therapeutic use; D001938:Brazil / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D058872:Epidemics; D005260:Female; D006785:Hospitals, University; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics / Q000302:isolation & purification*; D007251:Influenza, Human / Q000175:diagnosis / Q000188:drug therapy / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D053139:Oseltamivir / Q000627:therapeutic use; D011159:Population Surveillance / Q000379:methods*; D011446:Prospective Studies; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012621:Seasons; D055815:Young Adult
chemical_list: D000998:Antiviral Agents; D053139:Oseltamivir