Vector-borne disease

A vector-borne disease is transmitted to humans by an intermediate organism — most often a blood-feeding arthropod such as a mosquito, tick, flea, sandfly, or tsetse fly. The vector picks up the pathogen during one blood meal and transmits it during a subsequent meal, sometimes after the pathogen has multiplied or developed within the vector. Vector competence is a property of specific species: not every mosquito carries every mosquito-borne pathogen.

Major vector-borne diseases include malaria (Anopheles mosquitoes / Plasmodium parasites), dengue and Zika (Aedes mosquitoes / flaviviruses), Lyme disease (Ixodes ticks / Borrelia bacteria), West Nile virus (Culex mosquitoes), and yellow fever (Aedes / yellow fever virus). The WHO estimates vector-borne diseases account for more than 17% of all infectious diseases, with malaria alone responsible for over 200 million cases annually.

Vector-borne diseases differ from directly zoonotic diseases like hantavirus and Ebola in that they require a competent vector population to sustain transmission. Vector control — insecticide-treated bed nets, larvicidal applications, environmental management of breeding sites — is the operational backbone of vector-borne disease response. Climate, urbanization, and human movement materially shape vector range, which is why vector-borne disease distribution maps shift over decades.