The Marin/Sonoma Mosquito and Vector Control District announced that an adult mosquito sample from western Santa Rosa tested positive for West Nile virus. According to statistics maintained by the California Department of Public Health, this is the first such reported case in Sonoma County. Marin County still has no reported samples of the deadly virus. “We encourage residents to report mosquito problems and/or potential mosquito breeding areas so that we can do everything possible to prevent the spread of West Nile virus,” said District Manager Jim Wanderscheid in a statement. Residents are encouraged to be wary that the insects are more active during dawn and dusk, to use repellent, to ensure all windows and screens are in good condition, to cover septic tanks and screen roof vent pipes, and to eliminate sources of standing water on properties.