Quantitative analysis of respiratory viral triple infections: Examining within host dynamics of Influenza, RSV, and SARS-CoV-2

Prior research has explored co-infections that involve two respiratory viruses, yet triple infections remain poorly elucidated. With the COVID-19 pandemic and seasonal epidemics of respiratory syncytial virus (RSV) and influenza, understanding the dynamics of triple infections is critical for public health preparedness. The simultaneous circulation of influenza A virus (IAV), RSV, and SARS-CoV-2 presents a significant public health burden, particularly among vulnerable populations such as children, the elderly, and immunocompromised individuals. Comprehending the interactions among these viruses is crucial to improve our capacity to forecast and curb disease outbreaks. This study addresses the escalating concern over the interaction of multiple respiratory viruses by introducing a simple mathematical model to analyze triple infection dynamics involving IAV, RSV, and SARS-CoV-2. The central question addressed in this study is how variations in infection rates influence each virus's duration and peak viral load in a triple-infection scenario. We find distinct regimes where each virus can dominate and suppress the viral load and duration of the remaining two viruses. We derive an analytical expression for the dependence of the critical infection rate of one virus on the infection rates of the other two viruses. While the model will need to be extended to realistically capture in vivo viral dynamics, this analysis helps provide insight into the complex dynamics of multiple virus infections.