Characterizing potential interaction between respiratory syncytial virus and seasonal influenza in the U.S.

RSV and seasonal influenza are two of the most prevalent causes of respiratory infection in the U.S. In this study, we used weekly positive case reports and genetic surveillance data to characterize the circulation of these viruses in the United States between 2011 and 2019 and a mathematical modeling approach to explore their potential interaction at a regional level. Our analyses showed that RSV and seasonal influenza co-circulate with different relative epidemic sizes and seasonal overlaps across regions and seasons. We found that RSV had a different evolutionary dynamic compared to seasonal influenza and that local persistence may play a role in underlying annual epidemics. Our analysis supports a potential competitive interaction between RSV and seasonal influenza in most regions across the United States. The multiple-pathogen modeling framework suggests that cross-immunity following infection of either virus might be one of the key drivers of viral competition. However, this finding is based on model-derived inferences and limited surveillance data; further investigation is needed to confirm its robustness and gain a better understanding of the underlying mechanisms. These findings underscore the importance of continued research into the immunological and ecological mechanisms of viral inference, which might be important for the development of more effective protective strategies against co-circulating respiratory viruses.