Exploring RSV transmission patterns in different age groups in the United States.

Respiratory syncytial virus (RSV) infections are a significant public health concern for pediatric populations and older adults, with seasonal winter outbreaks in the United States (US). Little is known about the timing of RSV epidemics across age groups and the relative contribution of within-group and between-group transmission of RSV in each age group. The lack of understanding of age-specific RSV transmission patterns limits our ability to inform vaccination policies. In this study, we examine the timing and transmission patterns of RSV epidemics across different age groups in 12 US states from 2018 to 2024. We found that infants under 1 year and young children aged 1-4 years experienced the earliest epidemic timing, while the elderly group had the latest. Using a semi-mechanistic age-structured spatiotemporal model, we further showed that between-group transmission greatly contributes (>50%) to the burden of RSV hospitalizations for children under 1, school-age children aged 5-17, and adults aged 18-64. By contrast, incidence in the elderly group (above 65 years) was primarily driven by transmission within the age group. Our findings indicate that distinct age groups play unique roles in propagating RSV epidemics in the US, with age-specific transmission patterns that can guide more effective RSV vaccination policies.