In epidemiology, a vector is an organism that does not cause disease itself but that transmits infection by conveying pathogens from one host to another, serving as a route of transmission. A classic example is the anopheles mosquito, which acts as a vector for the disease malaria by transmitting the malarial parasite plasmodium to Humans. In this case plasmodium is harmless to the mosquito (its intermediate host) but causes the disease malaria in Humans (its definitive host). In molecular biology and genetic engineering, a vector is a vehicle for transferring genetic material into a cell.