The fact that humans and other mammals are considered dead end hosts for WNV, is a transmission problem (4). In this case, the virus is warded off by the host immune response and the host does not establish a significant viremia. Some mammalian host infections by WNV result in little more than headaches or a slight fever, depending on the immunity of the individual. In the extreme case the host is severely affected by the virus and death follows infection, ending the circulation of the virus and any potential for further spreading. Death in humans is closely linked to a compromised immune system, usually in the elderly or children (2,5). .
If we were to categorize this virus's ability to survive and thrive in multiple hosts by its ecology, it would be limited to those vertebrates that are easily accessible to the mosquito vector that transmits it. Vertebrate hosts living near swamps and locations where mosquitoes reside are at a higher risk of acquiring an infection. As mentioned earlier, those that are immunocompromised are more susceptible to infection of WNV. The virus survives in the environment by both mosquito and avian hosts. The mosquito host does not develop any symptoms from infection with WNV, permitting uninhibited propagation of virion. Migrating bird populations are becoming increasingly infected by the virus. These migratory birds are thought to be key spreading factors for the virus because they tend to move from one location to another. Some of the avian hosts are able to maintain a high titer of WNV and remain asymptomatic. This is considered to be a major transmission route as many of the birds don't die, but are replicating reservoirs for the virus (4). Many of the avian species, like Crows and Jays, are considered dead end species because the virus terminates with the host. .
With the present data on this virus, a conclusion can be made that WNV infects mosquitoes and vertebrate hosts.
