Characterization of Circulating RSV Strains Among Patients In The Outsmart RSV Program During the 2015–16 Winter Viral Season in the United States

BACKGROUND: Respiratory syncytial virus (RSV) is an established cause of serious lower respiratory tract disease in infants and young children. To better describe currently circulating strains, monitor their evolution and characterize the patient populations, the METHODS: OUTSMART included 14 labs in 4 US regions and Puerto Rico that provided RSV-positive samples and matching demographic data during Dec 2015 to Mar 2016 for subtyping and descriptive analyses. To gauge the representativeness of the OUTSMART patient sample, results were compared with the Nationwide Emergency Department Sample (NEDS) and the National Inpatient Sample (NIS). RESULTS: Participating labs reported 10,304 RSV-positive samples (10.9%) out of 94,710 tested, of which 525 samples were submitted for further analyses. The majority of samples came from children ≤ 2 years: 1–3 months (17.5%), 4–6 months (13.7%), 7–12 months (21.9%), and 1–2 years (17.5%). The distribution of samples from males (53.0%) and females (47.0%) were similar. Of those with determined RSV subtype (n = 392; 74.7%), 62.8% were subtype A and 38.3% were subtype B. Of the two co-circulating subtypes, A was more prevalent through age 5 while B was more common in those ages 6+. Hospitalizations >24 hours occurred among 36.6% of patients. The proportions of patients with subtype A were similar among hospitalized vs. non-hospitalized patients (62.3% and 63.2%, respectively). Subtype A predominated in all 4 regions, with the highest proportions of subtype A in the Midwest (65.1%) and the West (64.8%). Most RSV-positive samples were collected February- March. For all databases, the largest disease burden was among those <1 year old (OUTSMART: 45.1%, NEDS 62.3%, NIS 62.7%), followed by the 1–2 year age group (OUTSMART: 27.6%, NEDS 26.9%, NIS 21.8%). The databases were also similar by gender (% male–OUTSMART: 53.0%, NEDS 53.9%, NIS 53.9%). CONCLUSION: The OUTSMART program characterizes circulating RSV strains and monitors their temporal and geographic evolution in the US to inform the development of anti-RSV monoclonal antibodies and vaccines. DISCLOSURES: S. Pastula, AstraZeneca: Research Contractor, Research support; E. Levin-Sparenberg, AstraZeneca: Research Contractor, Research support; X. Jiang, AstraZeneca: Research Contractor, Research support; J. P. Fryzek, AstraZeneca: Research Contractor, Research support; J. Hackett, AstraZeneca: Employee, Salary; T. Villafana, Medimmune: Employee and Shareholder, Salary; L. Yu, Medimmune: Employee, Salary; M. T. Esser, MedImmune: Employee and Shareholder, Salary; A. Tovchigrechko, MedImmune: Employee and Shareholder, Long-term incentive stock grant and Salary; B. Lu, Medimmune: Employee, Salary; A. Ruzin, Medimmune: Employee and Shareholder, Salary