Pandemic influenza A(H1N1) 2009 and respiratory syncytial virus associated hospitalizations.

OBJECTIVES: To determine the contribution of influenza and respiratory syncytial virus (RSV) as the cause of lower respiratory tract infection (LRTI) associated hospitalizations during the first year of the influenza A(H1N1) 2009 pandemic and to assess the severity of illness during the second pandemic wave. METHODS: Patients admitted with LRTI from April 2009 through March 2010 were assessed for the presence of influenza and RSV. Pandemic influenza virus was detected by means of a nested RT-PCR assay and/or the CDC's real time-PCR protocol. RSV was detected using a one-step RT-PCR assay. The characteristics of patients admitted during the first and second pandemic outbreaks were compared. RESULTS: 657 patients with LRTI were admitted during the study period. Pandemic influenza virus was detected in 180 and RSV in 133. Influenza was the most common cause of infection in adults, while RSV was more common in children. There were no differences in disease severity between the first and second pandemic outbreaks. CONCLUSIONS: Pandemic influenza virus was associated to increased numbers of hospitalizations and deaths; particularly in adults. The severity of the first and second pandemic outbreaks was similar. RSV continues to be the main pathogen responsible for hospitalizations in young children.