Relating in vivo RSV infection kinetics to host infectiousness in different age groups.

Respiratory syncytial virus (RSV) infections are a major public health concern for pediatric populations and older adults. Viral kinetics, the dynamic processes of viral infection within an individual over time, vary across different populations. However, RSV transmission in different age groups is incompletely understood from the perspective of individual-level viral kinetics. Using a mathematical model and a hierarchical Bayesian framework, we analyzed viral kinetics in 53 individuals from different age groups to estimate infection parameters and linked within-host viral load to transmission probability through a probabilistic model. We found that children had higher peak viral loads and longer shedding periods compared to other age groups, suggesting a higher transmission probability over the infectious period. We validated our findings by comparing the estimated secondary attack rate across different age groups to empirical estimates from household transmission studies. Our work highlights the importance of age-specific considerations in understanding and managing RSV infections.