Clinical characteristics of children and adults hospitalized for influenza virus infection.

BACKGROUND/PURPOSE: Influenza infection has different clinical presentations and outcomes in children and adults, and bacterial coinfection is associated with significantly higher morbidity and mortality. This study compared the clinical features in children and adults hospitalized for influenza virus infection and the role of concomitant bacteremia. METHODS: A retrospective observational cohort study was conducted by a review of medical records of all consecutive patients admitted for influenza infection between April 1, 2009 and February 28, 2011. RESULTS: Of the 1203 patients, 76.2% were children, and ranged in age from 1 month to 99 years, with a mortality of 3.1% for adults; no children died. Pneumonia, acute respiratory distress syndrome, acute respiratory failure, septic shock, and cardiovascular complications were more common in adults. Bacteremia was more common in adults than in children (3.5% vs. 0.4%). C-reactive protein (CRP) > 4 mg/dL and a longer hospital stay occurred more often in children with bacteremia than in the group without bacteremia. In adults with bacteremia, acute respiratory failure, septic shock, and cardiovascular complications were more common, with a mortality of 50% versus 1.4% compared with those without bacteremia, and thrombocytopenia and increased CRP were independent risk factors. Using receiver operating characteristic analysis, CRP ≥ 14 mg/dL had a sensitivity of 90.0% and a specificity of 80.0%. CONCLUSION: Influenza infection in adults is associated with increased risk of complications, bacteremia, and mortality compared with that in children. Bacteremia in adults with influenza is associated with increased complications and mortality; thrombocytopenia and elevated CRP levels could identify those at risk.