VIRAL ENCEPHALITIS

New, clean chicken flocks are placed out each spring. Over the following months some become infected, showing places where the mosquitoes are transmitting encephalitis viruses from wild birds. These are areas where mosquito control is especially important, to help prevent transmission of Western Equine Encephalitis or Saint Louis Encephalitis viruses to local human residents. Infection rates can be much higher in some years.

Note: This figure is adapted from recent maps issued weekly by the California Mosquito Control Association. The current map and information on California's vector-borne disease surveillance system can be found at the Mosquito Net Home Page.