Malaria is a vector-borne disease, yes, in that insects carry it from one host to another. But vectors are not hosts; they belong to a different ecological category from, say, reservoirs; and they experience the presence of the pathogen in a different way. Transmission of malarial parasites from a mosquito to a human is not spillover. It’s something far more purposive and routine. Vectors seek hosts, because they need their resources (meaning, in most cases, their blood). Reservoirs do not seek spillover; it happens accidentally and it gains them nothing.
