RESUMO
OBJECTIVES: Two surges in influenza-like illness (ILI) visits to Children's Medical Center Emergency Departments, Dallas and Legacy, occurred in late spring (wave 1) and late summer 2009 (wave 2). This study describes respiratory viruses identified during the first weeks of waves 1 and 2 of the 2009 influenza A(H1N1) pandemic (pH1N1) and compares patients infected with pH1N1 with those infected with other respiratory viruses during wave 1. METHODS: From April 27 to May 7 and August 23 to September 7, 2009, nasopharyngeal swab specimens from all patients with temperature 38.2°C or higher plus 2 or more symptoms of ILI were tested by rapid antigen, direct fluorescent antibody, or multiplex polymerase chain reaction assays. Patients with pH1N1 during wave 1 were classified as cases and 3 age- and sex-matched controls were randomly selected from patients with 1 respiratory virus other than pH1N1. Odds ratios (ORs) and associated 95% confidence intervals (95% CIs) of characteristics associated with patients with pH1N1 were estimated using conditional logistic regression models. RESULTS: During wave 1, single viruses identified in 1023 symptomatic children were confirmed pH1N1 (55, 5.4%), rhinovirus (505, 49.4%), parainfluenza 3 (199, 19.5%), and human metapneumovirus (169, 16.5%). By multivariable analysis, duration of fever (OR, 1.49; 95% CI, 1.02-2.20) and myalgia at presentation (OR, 3.09; 95% CI, 1.09-8.76) were independent predictors associated with pH1N1. During wave 2, 114 (59.7%) of single viruses were pH1N1. CONCLUSIONS: During the epidemic of ILI in Spring 2009, other respiratory viruses were identified more frequently than pH1N1 influenza in children with ILIs. Clinical presentation was similar for all respiratory viruses. Molecular diagnostic testing can define the prevalent viruses during community outbreaks and provide guidance to physicians making treatment decisions in emergency departments.