title: Impact of the novel influenza A (H1N1) during the 2009 autumn-winter season in a large hospital setting in Santiago, Chile.
abstract: BACKGROUND
  In Chile, the novel influenza A (H1N1) epidemic began in the middle-high income area of Santiago. Clinical and laboratory surveillance was intensified with the aim to characterize the epidemic and determine its impact in a large hospital setting.
  
  
  METHODS
  Demographic and clinical data were obtained from all patients whose symptoms met the clinical definition of influenza A (H1N1) infection during the epidemic period. Laboratory confirmation was obtained by use of a nasopharyngeal antigen detection test for influenza A and/or influenza A (H1N1) polymerase chain reaction (PCR). A case was considered confirmed if the antigen detection test result for influenza A and/or the PCR test result were positive.
  
  
  RESULTS
  The total number of emergency department (ED) visits increased by 88.5% from a mean of 14,489 ED visits in 2006-2008 to a mean of 27,308 ED visits in 2009, during the epidemic period. There were 10,048 patients who were clinically diagnosed with influenza A (H1N1), and they represented 78% of all visits, of which 4591 (45.6%) were laboratory confirmed. The median time from symptom onset to diagnosis was 1 day, and 99.7% of individuals received antiviral treatment. School-aged children represented 67% of ED visits at the beginning of the epidemic and 24% of ED visits at the end of the epidemic. Only 2% of cases were hospitalized; of these, 70% of cases occurred in patients 6-50 years of age, and 32% of cases occurred in patients who had an underlying medical condition. Eleven patients (age range, 1-53 years) required admission to the intensive care unit (ICU); 6 of these patients had pneumonia with or without hemodynamic shock. No influenza-associated deaths occurred.
  
  
  CONCLUSIONS
  Many cases of influenza A (H1N1) occurred in school-aged and adult individuals who required an ED visit; these visits resulted in a low impact on the use of hospital beds. Aggressive ICU management and/or experience in extracorporeal membrane oxygenation significantly improved outcomes. Early antiviral treatment may have played an important role in the low number of severe cases. Vaccines targeted for school-aged children and young adults may modify the first epidemic wave in the northern hemisphere.
authors.affiliation: Department of Pediatrics, Division of Pediatric Infectious Diseases, Faculty of Medicine, Universidad de Chile, Santiago, Chile. jptorres@clc.cl
authors.forename: Juan Pablo
authors.initials: JP
authors.lastname: Torres
authors.forename: Miguel
authors.initials: M
authors.lastname: O'Ryan
authors.forename: Beatrice
authors.initials: B
authors.lastname: Herve
authors.forename: Ricardo
authors.initials: R
authors.lastname: Espinoza
authors.forename: Guillermo
authors.initials: G
authors.lastname: Acuña
authors.forename: Jaime
authors.initials: J
authors.lastname: Mañalich
authors.forename: May
authors.initials: M
authors.lastname: Chomalí
mesh_terms: D000293:Adolescent; D000328:Adult; D000956:Antigens, Viral / Q000032:analysis; D000998:Antiviral Agents / Q000627:therapeutic use; D002648:Child; D002675:Child, Preschool; D002677:Chile / Q000453:epidemiology; D004636:Emergency Service, Hospital; D005260:Female; D006761:Hospitals; D006801:Humans; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype / Q000302:isolation & purification*; D007251:Influenza, Human / Q000453:epidemiology* / Q000473:pathology / Q000628:therapy / Q000821:virology*; D008297:Male; D008875:Middle Aged; D009305:Nasopharynx / Q000821:virology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D055815:Young Adult
chemical_list: D000956:Antigens, Viral; D000998:Antiviral Agents