WEE a disease that is spread to horses and humans by infected mosquitoes. WEE is caused by the western equine encephalitis virus, an arbovirus.
Arbovirus is short for arthropod-borne virus.
In North America, arboviruses are usually spread by infected mosquitoes. Birds are often the source of infection for mosquitoes, which can sometimes spread the infection to horses, cattle, pigs, dogs, emus, ostriches, and, in rare cases, people. The virus that causes western equine encephalitis has a complex life cycle involving birds and a specific type of mosquito, Culex tarsalis , that is common in farming areas and around irrigated fields. Humans, horses, and other mammals are not an important part of the life cycle of the virus. In rare cases, however, people who live in or visit an area where the virus lives can be infected by the bite of an infected mosquito.