West Nile Virus is maintained in what cycle, and which birds show high mortality?

• A. Bird-to-bird cycle; high mortality in sparrows and pigeons
• B. Mammal-to-mammal cycle; high mortality in deer
• C. Bird-to-bird cycle; high mortality in crows, jays, hawks, owls
• D. No mortality in birds; only affects humans

Answer: (C)

West Nile virus is maintained in a bird-to-bird cycle in nature, with mosquitoes acting as the agents that transfer the virus from one bird to another. Birds develop enough virus in their blood to infect biting mosquitoes, which then bite more birds and continue the cycle. Some bird species are highly susceptible, leading to high mortality in corvids such as crows and blue jays, and also in some raptors like hawks and owls. Humans and horses can become infected but do not sustain transmission, so they’re considered dead-end hosts. The other options don’t fit because the virus isn’t maintained primarily in mammals, and there are well-documented bird die-offs rather than no mortality in birds.