Respiratory syncytial virus seasonality in southeast Florida: results from three area hospitals caring for children.

Southeast Florida generally experiences longer seasonal epidemics of respiratory syncytial virus (RSV) than other parts of the country. In this report, the primary objective was to more accurately define the onset, peak, and duration of the RSV season in Southeast Florida. The results obtained for this region were also compared with those reported for the state and for the nation. Seasonal patterns for RSV in Southeast Florida were analyzed based on the total number of RSV tests performed, number of positive tests, and percent of positive tests in children presenting with bronchiolitis to 3 emergency departments from January 2003 through December 2006. RSV was detected by rapid diagnostic testing and considered to be present at epidemic levels when at least 10% of performed tests were positive during a given month. During the entire 12 months of 2003 and 2006, RSV was detected above epidemic levels. The RSV-detection test positivity rate was less than 10% in only 6 months of 48 total months of observation, but during the months that were below epidemic threshold, RSV was still frequently identified. RSV activity increased during July, peaked during October, and waned during the spring months. These findings were nearly identical to those recently reported in other studies, confirming that RSV circulated at epidemic levels in Southeast Florida during most of the 4-year observation period and remained a significant cause of respiratory disease and hospitalization throughout the year. Strategies for RSV prophylaxis in at-risk children in South Florida should consider results of local RSV test detection.