Hello!
The mosquito played the role of vector in the chain of transmission.
Definition of vector: Vectors are like bridges that carry germs into people or other living things, either by touching them directly or indirectly.
Jane's skin is the 'portal of entry' for the mosquito, just like a door. Jane herself is both the 'susceptible host' (where the infection will live and grow) and the 'reservoir' (where the infection comes from). So, the mosquito is carrying an infection and lands on Jane's skin, which is where the infection gets in and lives.