Respiratory Syncytial Virus Seasonality - United States, 2014-2017

What is already known about this topic? For most of the United States, the respiratory syncytial virus (RSV) season lasts from fall through spring but varies from year to year and by geographic region. What is added by this report? This report uses a new statistical method that analyzes polymerase chain reaction laboratory detections reported to the National Respiratory and Enteric Virus Surveillance System (NREVSS) to determine RSV seasonality nationally and by region for three recent seasons (2014-2017). Nationally, lasting from the week ending July 5, 2014 through July 1, 2017, the median RSV onset occurred at week 41 (mid-October), and lasted 31 weeks until week 18 (early May). The median national peak occurred at week 5 (early February). Onsets for the 2014-17 seasons occurred approximately 2 weeks earlier than did those for the 2012-2014 seasons (early to mid-October versus late October to early November), which were determined using antigen data. What are the implications for public health practice? RSV seasonality data can guide diagnostic testing and inform policy decisions regarding administration of currently available immunoprophylaxis products, when indicated, and the timing of clinical trials and future evaluations of vaccines and immunoprophylaxis products currently under development.