Which of the following is NOT vectored by ticks?

West Nile virus is primarily transmitted by mosquitoes, not ticks. This viral infection is spread to humans through the bite of infected mosquitoes, particularly Culex species. While the other diseases listed—Rocky Mountain spotted fever, human ehrlichiosis, and Lyme disease—are indeed transmitted through tick bites, West Nile virus does not involve ticks in its transmission cycle.

Understanding the specific vectors for different diseases is crucial in public health for prevention and control strategies. Knowing that West Nile virus is not associated with ticks helps clarify the importance of monitoring and controlling mosquito populations in areas where this virus is prevalent.