Abstract: Understanding the interactions between infected and susceptible individuals is essential in disease management and prevention. Two common transmission routes are vector borne transmission (e.g., transmission via arthropods) and environmental transmission (transmission via infectious propagules shed into the environment). Differences in transmission mode could potentially lead to different population-level outbreak patterns. In particular, vector-transmitted pathogens could produce very different patterns depending on the life-history and demography of the vector. The goal of this study is to explore when vector-transmitted pathogens have similar versus different population-level epidemiological dynamics as environmentally transmitted pathogens. Our approach is to analyze SIR-type models of vector-transmitted diseases and use a quasi-steady-state approximation (QSSA) to determine when vector-transmission models reduce down to forms identical to and distinct from environmental transmission models. Our results show that some vector transmission models can reduce down to environmental transmission models. One such scenario is when vector reproduction is tightly tied to the vector-host interaction, e.g., vector reproduction requires taking a blood meal from the host, and that blood meal is when transmission occurs. In conclusion, our study identifies when differences in the pathogen transmission mechanism can potentially lead to different population-level disease outbreak patterns. This helps identify when it may be feasible or infeasible to infer the transmission mechanism from population-level time series data.
