In epidemiology, a disease vector is any living[1] agent that carries and transmits an infectious pathogen such as a parasite or microbe, to another living organism.[2][3] Agents regarded as vectors are mostly blood-sucking insects such as mosquitoes. The first major discovery of a disease vector came from Ronald Ross in 1897, who discovered the malaria pathogen when he dissected the stomach tissue of a mosquito.[4][5][dead link ]