The Centers for Disease Control and Prevention has now counted 504 human West Nile virus cases across 41 states this year, and 363 of them, about 72 percent, are the neuroinvasive form in which the virus reaches the brain or spinal cord.
Those figures come from the CDC's ArboNET surveillance system, current through Sept. 8 and compiled in a survey report from the Annenberg Public Policy Center at the University of Pennsylvania. The agency refreshed its current-year West Nile dashboard again on Sept. 15. The severity share is higher than at the same point last year, when 490 of 771 reported cases, roughly 64 percent, were neuroinvasive.
