Resource burden at children's hospitals during the spring 2009 H1N1 pandemic

Objective: Describe the ED utilization burden of the April- July 2009 H1N1 influenza pandemic at tertiary care children's hospitals in the US by quantifying observed utilization as a proportion of expected utilization. Methods: We used the Pediatric Health Information System database of emergency department (ED) visits for 23 children's hospitals, using data from April-July 2009, with data from the corresponding weeks of 2004-08 as comparison. Observed weekly ED visits for influenza-like illness (ILI) were calculated using previously-validated ICD-9 codes for ILI. A time series was fit to the 2004-08 data to generate expected weekly values for 2009. The start and end of each ED's surge period was defined by the first and last 2 adjacent weeks with observed ED ILI visits above the upper 95% confidence limit for the expected value. For each ED, we report the surge duration, and the observed:expected ratio for ED visits, ED ILI visits, necessary ED visits, admissions, deaths, and influenza-related tests, medications, and procedures. Results: Of the 23 EDs, 13 experienced a surge in ED ILI visits. The median surge duration was 2 weeks, with an interquartile range (IQR) of (0, 5). The median (IQR) observed:expected ratio for ED ILI visits was 1.42 (1.32, 1.61). The median (IQR) observed:expected ratio for the peak week was 1.88 (1.52, 2.11). Conclusions: The Spring 2009 H1N1 influenza surge was experienced by most children's hospital EDs. Surge magnitude and duration varied, but, at its peak, the EDs experienced a median ED ILI visit rate of 88% above expected utilization.