13. How the Transmission Cycle Works
Don’t think that the disease originates in mosquitoes; they’re only carriers. They receive the virus by biting infected birds. Sometimes, if a bird has high levels of the virus, the mosquito will transmit this to other birds, as well as other mammals, including humans. Thankfully, these mammals are not capable of producing high-enough levels of the virus for it to be passed on through other mosquitoes.
More than 300 species of bird have at some point become infected with West Nile virus. The infection can kill species like the greater sage-grouse, American crow, and blue jay. Some North American birds, including the wood thrush, northern cardinal, and brown thrasher, have high levels of antibodies that can protect against West Nile virus.