2328. Human Respiratory Syncytial Virus Subgroups among Hospitalized Infants in the United States, 2015–2016

Background Respiratory syncytial virus (RSV) is a major cause of severe acute respiratory illnesses (ARI) in young children. Circulation of RSV subgroups A and B can vary by season and geographic location, and may have implications for disease susceptibility, outcomes, and prevention measures. We investigated RSV subgroup distribution among samples collected in the New Vaccine Surveillance Network. Methods Prospective active surveillance for hospitalized ARI was conducted from November 1, 2015 to June 30, 2016 among children < 12 months of age at seven pediatric hospital sites. Mid-turbinate nasal and throat flocked swabs (combined when both available) and/or tracheal aspirates were collected and tested for RSV at each site using real-time reverse transcription polymerase chain reaction (rRT–PCR) assays; RSV A/B subgroup results were available from four sites that did their own subgroup testing (Cincinnati, Kansas City, Houston, and Oakland). At three sites (Rochester, Nashville, Seattle), approximately 50 RSV-positive specimens were sampled based on the monthly distribution for each site and 1:1 distribution by gender, and then assayed for subgroup at CDC. Patient information was obtained from medical records; chi-square tests were used to compare the distribution of A and B subgroups by site. Results Of 704 RSV-positive hospitalized infants, subgroup data from 586 were analyzed; 340 (58%) were RSV A and 246 (42%) were RSV B. The median age for both RSV A and RSV B patients was 2 months. Subgroup distribution varied by geographic location, with the overall proportion of RSV A ranging from 18–83% across sites (P < 0.01). Peak RSV A and B detections by month varied by site, occurring from November–February (figure). Conclusion During the 2015–2016 season, RSV A and B subgroups co-circulated among hospitalized infants enrolled at seven US sites. The predominance of RSV subgroup varied by geographic location. Continued surveillance and additional subgroup testing over multiple seasons should improve understanding of the epidemiologic significance of RSV infections by subgroup. Disclosures All authors: No reported disclosures.