Heat and habitat shifts push California toward a vector-borne disease hotspot

Rising temperatures and climate-driven changes are expanding vectors—mosquitoes, ticks, fleas—in California, fueling West Nile virus activity in birds and humans, signaling growing dengue risk in urban areas, and contributing to flea-borne typhus outbreaks. Experts emphasize there isn’t a single cause; rather a mix of warming, habitat disruption, and ecosystem changes that are increasing opportunities for disease transmission statewide.