Vector-borne diseases
Vector-borne disease models represent transmission between a host population and a transmitting vector such as a mosquito or tick.
Two linked populations
Transmission commonly occurs through a cycle
\[\text{infectious host}\to\text{susceptible vector}\to\text{infectious vector}\to\text{susceptible host}.\]Host and vector populations therefore require separate state variables.
Transmission terms
Rates depend on quantities such as biting rate, vector abundance, infection prevalence and probabilities of transmission per bite.
Why ordinary SIR structure is insufficient
Direct host-to-host transmission is not the main mechanism, so vector dynamics and the coupling between host and vector infection must be represented explicitly.
Key idea. Vector-borne models describe a transmission cycle across two interacting populations rather than a single host population.