Environmental Management

Carla B. Hass



Recent Weather Creates Perfect Conditions for Mosquitoes

(PLACERVILLE, CA) – The California Legislature has declared April 21stth through April 27th, 2019 as Mosquito Awareness Week to raise awareness and educate Californians about the threat mosquitoes pose to our communities.  El Dorado County health officials are reminding residents to take steps to protect themselves from mosquitoes as warmer weather approaches, both at home and when traveling out of the Country, and to be aware of the serious risks mosquitoes present to their health including West Nile, Saint Louis encephalitis, dengue, chikungunya, and Zika viruses.


West Nile Virus (WNV) and St. Louis Encephalitis (SLEV) are primarily diseases of birds that can be transmitted to people and animals by mosquitoes.  Both are mosquito-borne diseases that can result in debilitating cases of meningitis and encephalitis and death to humans, horses, avian species and other wildlife.  In 2018, there were 218 confirmed human cases of WNV in 31 counties throughout California with no cases in El Dorado County.  Statewide there were 8 human deaths.  The most recent human case of WNV in El Dorado County was in 2016.  St. Louis encephalitis has not been detected in El Dorado County but is present in Northern California and can be transmitted by mosquitoes commonly found in California (Culex species).


The other three illnesses are primarily associated with travel outside the U.S.  "Pregnant women should be aware about the risks of traveling to Mexico and other countries where the Zika virus can be transmitted through mosquito bite, which can result in harm to the growing fetus," said County Health Officer, Dr. Nancy Williams.  "Babies born to mothers infected with Zika virus can be born with microcephaly or other severe fetal brain defects.  The safest thing for pregnant women or women who could become pregnant is to postpone travel to countries where Zika virus is present until after the baby is born."  For more information about Zika virus and pregnant women, Williams points people to


El Dorado County Vector Control technicians respond to resident complaints and provide surveillance and control of mosquito sources in designated areas of El Dorado County.  Residents and visitors can reduce their risk of mosquito-borne diseases by taking the following precautions:


  • Eliminate or drain all sources of standing water around your property including flower pots, old tires, and buckets. Mosquitoes can lay their eggs in sources of water as small as a bottle cap.
  • Avoid activity outside when mosquitoes are most active, especially at dawn and the first two hours after sunset. If you are being bitten or see any other activity outside these time frames, please contact Vector Control.
  • If you are outdoors when mosquitoes are biting, wear long pants and long-sleeved shirts.
  • Apply insect repellent containing EPA-registered active ingredients such as DEET, Picaridin, IR3535, or Oil of lemon eucalyptus.  Always apply according to label instructions.
  • Make sure doors and windows have tight-fitted screens. Repair or replace screens that have tears or holes.
  • If planning travel out of the Country, check with the Centers for Disease Control at for current information and advisories related to Zika, yellow fever, and other travel-related risks.


To report a dead bird, contact the West Nile Virus Hotline at 1-877-WNV-BIRD (1-877-968-2473) or visit their website   To report a complaint about mosquito activity contact El Dorado County Vector Control at (530) 573-3197 in the Tahoe Basin, or (530) 621-5300 on the West Slope.  For more information, please visit Environmental Management Department's Vector Control page




Providing safe, healthy and vibrant communities; respecting our natural resources and historical heritage.