Influenza A infection in young infants.

OBJECTIVE To determine the clinical characteristics of infants ≤2 months old hospitalised with influenza A. STUDY DESIGN The study was a retrospective analysis of infants ≤2 months old hospitalised with fever, respiratory distress and/or sepsis. Clinical signs, laboratory values, hospital duration and outcome were compared between children with influenza A and other viruses. RESULTS The charts of 268 infants were reviewed. 29 (11%) children had laboratory-confirmed influenza A infection. Unique features associated with influenza infection included the high number presenting with fever (97%) and a history of exposure to family members with a flu-like illness (69%). A significantly lower rate of respiratory distress was observed in the influenza group compared with respiratory syncytial virus (RSV) (24% vs 89%, p≤0.001). Median duration of hospitalisation for influenza was shorter than RSV (4 days vs 6 days, p<0.001). CONCLUSIONS In young infants, influenza A is a relatively mild disease compared to RSV and is primarily associated with upper respiratory tract manifestations.