Which animals are known to be reservoirs for the viruses causing West Nile virus or St. Louis encephalitis?

Certain birds are recognized as key reservoirs for the viruses that cause West Nile virus and St. Louis encephalitis. This is primarily because these viruses replicate well within bird populations, allowing for a significant viral load to circulate in their bloodstream. When mosquitoes feed on these infected birds, they can then transmit the viruses to other animals, including humans.

Birds, particularly corvids like crows and jays, are highly susceptible to these viruses and play a critical role in the ecology of their transmission. This connection between birds and mosquitoes is essential for understanding the life cycle of these viruses and the risk of human infections.

In contrast, reptiles, mammals, and amphibians do not have the same capacity to harbor these viruses or support their transmission effectively. While mammals can become infected by these viruses, they do not maintain sufficient levels of the virus in their systems to act as effective reservoirs for mosquitoes.