Epidemiology of respiratory syncytial virus in various regions within North Carolina during multiple seasons.

BACKGROUND: The Centers for Disease Control and Prevention (CDC) monitors the occurrence of respiratory syncytial virus (RSV) in the United States and has historically reported on activity at the regional level. Prior to the 2007-2008 RSVseason, the CDC did not report seasonal RSV data for cities within North Carolina or for the state. The purpose of the present study is to characterize RSV seasonal activity within North Carolina and to determine the appropriate months in which at-risk children should receive prophylaxis. METHODS: We prospectively collected RSV test data monthly over three seasons (fall through spring), from September 2003 through July 2006, from a diverse group of hospitals and a community pediatric practice located within five regions throughout North Carolina. RESULTS: Approximately 14,000 laboratory tests, including 23.7% that were RSV positive, were evaluated over the three seasons, and RSV was detected within the state during all but three months of the study. Seasonal variation in the onset (October-November) of RSV activity and duration (six to seven months) of the RSV season according to the specified definition of seasonality was noted yearly within individual regions and among regions. On average over the study period, the greatest percentage of positive tests (33.8%) statewide occurred during January. CONCLUSIONS: Our data suggest the RSV season in North Carolina is longer than the national average, and RSV epidemics persist during months that fall outside of those in which RSV prophylaxis is given to high-risk children. Guidelines on the administration of RSV prophylaxis should ideally be based on results of local RSV test data.