Background: Emergency department (ED) presentation of pediatric pandemic H1N1 (pH1N1) infection is not well characterized. Our objective was to describe the clinical manifestations of pH1N1 in the pediatric ED. We also compared these characteristics to seasonal influenza A, and explored risk factors for pH1N1 hospitalization.
Methods: We conducted a retrospective cohort study at a pediatric hospital in Quebec City, Canada. Subjects were ED patients aged 0 to 17 years with laboratory-confirmed pH1N1 (April–July 2009) or seasonal influenza A (June 2006–March 2009). Clinical and laboratory data were analyzed by univariate and multivariate log-binomial regression.
Results: A total of 127 pH1N1 cases and 110 seasonal influenza cases were identified. pH1N1 patients were older (9.5 vs. 5.6 years; P < 0.0001) and presented more rapidly (2.8 vs. 3.5 days; P = 0.02). Clinical manifestations were similar, although gastrointestinal findings were less frequent in pH1N1 (relative risk [RR]: 0.49; 95% confidence interval [CI]: 0.37–0.65). Hospitalization risk was similar (RR: 1.12; 95% CI: 0.81–1.55), but hospitalized pH1N1 subjects were more frequently diagnosed with pneumonia (RR: 2.41; 95% CI: 1.16–5.00). In a multivariable model, age <2 years was independently associated with pH1N1 hospitalization (RR: 3.17; 95% CI: 1.78–5.65), whereas the absence of significant comorbidities decreased its risk (RR: 0.51; 95% CI: 0.31–0.85).
Conclusions: After adjustment for age and delay to presentation, clinical manifestations and 21-day outcomes of pediatric pH1N1 were similar to those of seasonal influenza. pH1N1 patients with previously established risk factors for severe seasonal influenza experienced increased hospitalization risk. Our results suggest that pH1N1 clinical diagnosis and management in the pediatric ED can be performed in a manner similar to seasonal influenza.
From the *Centre de Recherche en Pédiatrie du CHUL (CHUQ), Quebec, Canada; †Centre de Recherche en Infectiologie du CHUL (CHUQ), Quebec, Canada; ‡Institut National de Santé Publique du Québec, Quebec, Canada; and §Department of Epidemiology and Biostatistics, McGill University, Montreal, Canada.
Accepted for publication January 13, 2011.
E.A. is the recipient of a training bursary from “Fondation des Étoiles”; Guy Boivin is the holder of the Canada Research Chair on emerging viruses and antiviral resistance, and is the Canadian Pandemic Team Leader on antiviral resistance and evolution of influenza viruses.
Address for correspondence: Guy Boivin, MD, MSc, CHUL, Room RC-709, 2705 Blvd Laurier, Quebec City, Quebec G1V 4G2, Canada. E-mail: Guy.Boivin@crchul.ulaval.ca.
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