Vector (epidemiology)

In epidemiology, a vector is a means by which an etiologic agent (i.e., the cause of morbidity or mortality) is transferred. Vectors can exist at different levels of indirection. For example, a mosquito of the genus Anopheles will bite a human infected with malaria, absorb Plasmodium falciparum or another malaria pathogen, and then fly to and bite another human, transferring the pathogen at that time. Plague is most frequently directly transmitted by a flea, Xenopsylla cheopis, but the key to stopping plague spread is killing the mammals, usually rats, which carry it from place to place.