Shift in the timing of respiratory syncytial virus circulation in a subtropical megalopolis: implications for immunoprophylaxis.

Respiratory syncytial virus (RSV) is the most common cause of severe respiratory infections worldwide, and an important cause of childhood bronchiolitis, pneumonia, and mortality. Although prevention of RSV infection by immunoprophylaxis with palivizumab has proved effective, a precise understanding of the timing of RSV outbreaks is necessary to ensure that infants are protected when RSV is circulating. In this study a consistent shift in the seasonal patterns of RSV circulation in southeast Brazil (São Paulo) is reported based on the analysis of 15 years of viral surveillance.