Final answer:
West Nile fever is primarily hosted by birds, with humans being dead-end hosts. Culex mosquitoes transmit the virus, which can cause symptoms ranging from none to severe neurological diseases. The virus spread rapidly across North America since its introduction in 1999.
Step-by-step explanation:
The hosts of West Nile fever are primarily birds, which serve as natural reservoirs for the virus. When Culex species mosquitoes feed on these infected birds, they become vectors and can transmit the virus to humans and other animals. While humans can become infected, it's important to note that humans are considered dead-end hosts for the virus, meaning that they do not contribute to the spread of the virus to feeding mosquitoes.
Infection in humans can range from asymptomatic to severe symptoms such as encephalitis or meningitis, with a mortality rate for those developing neurological disease around 10%. The first case of West Nile virus in North America was reported in 1999, and the virus has rapidly spread since, largely due to the migratory patterns of birds.