title: Pandemic H1N1 influenza in the pediatric emergency department: a comparison with previous seasonal influenza outbreaks.
abstract: OBJECTIVE
  We compare the acuity of pediatric emergency department (ED) patients between the ongoing H1N1 influenza pandemic and previous seasonal influenza outbreaks.
  
  
  METHODS
  An observational, cross-sectional analysis of patient visits at 2 pediatric tertiary care EDs was made for the following periods: (1) regional fall 2009 H1N1 influenza surge (August 17 to September 20, 2009), and (2) combined regional 2007 to 2009 early peak influenza seasons (January 28 to March 2, 2008, and February 2 to March 8, 2009). Proportions of admissions, return visits, and return visits resulting in admission were compared between the 2 periods. Subset analysis of patients with influenza-like illness was performed.
  
  
  RESULTS
  Of total visits, no difference was found in the proportions of hospital admissions between the 2009 H1N1 surge (18,503 visits) and the previous influenza seasons (29,002 visits): non-ICU 9.9% versus 10.4%, 95% confidence interval of the difference -0.07% to 1.0%; ICU 0.9% versus 0.9%, 95% CI of the difference -0.1% to 0.2%. Of patients with influenza-like illness, no difference was found in the proportions of non-ICU admissions between the 2009 H1N1 surge (7,064 visits) and the previous influenza seasons (8,489 visits): 4.8% versus 5.2%, 95% CI of the difference -0.3% to 1.1%, whereas the proportion of ICU admissions increased during the 2009 H1N1 surge: 0.3% versus 0.1%, 95% CI of the difference 0.05% to 0.4%. The proportions of return visits within 7 days, including those resulting in admission, were similar between the 2 periods for both the total ED population and the influenza-like illness subset.
  
  
  CONCLUSIONS
  The severity of illness during the 2009 H1N1 surge appeared similar to that of previous influenza seasons for the total population of the 2 pediatric tertiary care EDs, whereas an increase in the proportion of ICU admissions was observed for patients with influenza-like illness.
authors.affiliation: Department of Pediatrics, Division of Pediatric Emergency Medicine, Emory University School of Medicine, Atlanta, GA, USA. brian_costello@oz.ped.emory.edu
authors.forename: Brian E
authors.initials: BE
authors.lastname: Costello
authors.forename: Harold K
authors.initials: HK
authors.lastname: Simon
authors.forename: Robert
authors.initials: R
authors.lastname: Massey
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Hirsh
mesh_terms: D000367:Age Factors; D002648:Child; D002675:Child, Preschool; D016001:Confidence Intervals; D003430:Cross-Sectional Studies; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data*; D005260:Female; D005845:Georgia; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype; D007251:Influenza, Human / Q000453:epidemiology*; D008297:Male; D058873:Pandemics / Q000706:statistics & numerical data*; D012720:Severity of Illness Index