Officials urge residents to protect themselves from mosquito bites with an EPA-registered repellent 

ROSEVILLE, Calif., August 30, 2023 – Placer County’s public health officer, along with the Placer Mosquito and Vector Control District, are urging residents to prevent mosquito bites after the first human case of West Nile virus was reported in Roseville this week.

West Nile virus is a potentially serious illness transmitted through the bite of a female mosquito and there is no cure. “While most people with West Nile virus may not feel sick, or have mild symptoms, about 1 in 150 infected people develop a serious illness,” said Dr. Rob Oldham, the county’s interim health officer. “Taking simple measures to prevent mosquito bites can reduce this risk.”

This summer, the Placer Mosquito and Vector Control District has reported record numbers of West Nile virus detections in dead birds and mosquito samples throughout the county. As of this week, there have been 34 dead birds and 165 mosquito samples that have tested positive for West Nile virus.

The District traps and tests mosquitoes for West Nile virus weekly throughout the county during the summer and uses the test results to assess the risk of West Nile virus transmission to people, inform the public and make preventative or responsive vector control treatments in the most safe, timely and effective way possible to protect public health in Placer County. “We encourage residents to wear an EPA-registered repellent to protect themselves from mosquito bites while we enhance our surveillance efforts and schedule treatments to help lower the risk of disease transmission to people,” said District Manager, Joel Buettner. Although human cases are reported weeks after the onset of symptoms in patients, the risk for West Nile virus transmission to humans in Placer County remains high. The District and the county anticipate there will be more human cases reported as we exit summer and enter fall.

Officials recommend that people prevent exposure to mosquito bites and West Nile virus by practicing the “three Ds”:

  1. DEET – Apply insect repellent containing DEET, picaridin, oil of lemon eucalyptus or IR3535 according to label instructions. Repellents keep the mosquitoes from biting you. DEET can be used safely on infants and children 2 months of age and older.
  2. DAWN AND DUSK – Mosquitoes often bite in the early morning and evening so it is important to wear proper clothing and repellent if outside during these times. Make sure that your doors and windows have tight-fitting screens to keep mosquitoes out. Repair or replace screens with tears or holes.
  3. DUMP AND DRAIN – Mosquitoes lay their eggs on standing water. Eliminate all sources of standing water on your property, including flower pots, old car tires, rain gutters and pet bowls. If you know of a swimming pool that is not being properly maintained, please contact the district at 916-380-5444.

For more information about West Nile virus, visit the state of California’s website on West Nile. Residents are encouraged to report all dead birds on that website or by calling toll-free 1-877-WNV-BIRD (968-2473).

For more information about the Placer Mosquito and Vector Control District, contact the District at (916) 380-5444 or Follow the District on FacebookTwitterInstagram and TikTok: @placermosquito. For a list of EPA-registered repellents, please visit or