About 80% of people infected with West Nile virus never develop symptoms. There is no vaccine for West Nile virus in humans and no specific antiviral treatment. The central uncertainty is how far the human case count will climb during the two highest-transmission months of the year. July 21, 2026: CDC reports 91 human West Nile cases across 20 states nationally. Frequently Asked QuestionsWhich California counties have confirmed human West Nile cases in 2026?