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April 13, 2018 - Mosquito Threats on the Rise and Californians are Nurturing the Threat

Mosquito Awareness Week educates California residents on preventing mosquito-borne viruses

SACRAMENTO, CALIFORNIA  – There has been a steep rise in detections of invasive mosquito species in California, according to the California Department of Public Health, which increases the risk of local transmission of imported diseases. At the same time, lifted water restrictions in the state allows for the return to water practices by Californians that increase mosquito habitats.
Two invasive mosquito species, Aedes aegypti and Aedes albopictus, have been found in nearly 200 cities in Southern and Central California and continue to spread throughout the state. This is a sharp increase from just five years ago when only four cities reported one of the invasive mosquito species. Both invasive species are capable of transmitting viruses that are dangerous to people such as chikungunya, dengue, and Zika.
“With millions of international travelers arriving or returning to California each year and the spread of these invasive mosquito species across California, the potential for local transmission of imported diseases is increasing,” said David Heft, President of the Mosquito and Vector Control Association of California (MVCAC). “All it will take is one invasive mosquito biting one infected traveler for these diseases to potentially spread to others here at home. While surveillance and mosquito control activities are critical to protecting public health, the public also needs to do everything in their power to get rid of sources in their own communities where mosquitoes develop.”
Mosquito experts throughout the state stress the need for Californians to be aware of the serious health risks that mosquitoes pose and to take measures to reduce mosquito populations and protect themselves. Mosquito-transmitted diseases are the cause of death in hundreds of thousands of people every year worldwide and sicken millions more. To raise awareness and educate Californians about the public health threat mosquitoes pose to our communities, the California Legislature declared April 15-22, 2018 as Mosquito Awareness Week.
“All California residents play an important role in protecting public health and this is especially important as threats of mosquito-transmitted diseases continue to rise,” said Assemblymember Bill Quirk (D-20), author of Resolution HR 100. “Mosquitoes can lay their eggs in sources of water as small as a bottle cap, so it is critical that Californians are cognizant of their water use and take steps to diminish mosquito breeding potential.”
How Californians use water can increase mosquito habitats, intensifying the risk of disease transmission in residential areas. The State Water Resource Control Board is looking at regulating wasteful water practices by Californians, some of which promote mosquito breeding. They include:

  • over watering lawns in which water flows into the street
  • washing down driveways and sidewalks
  • washing your car using a hose without an automatic shutoff nozzle
  • watering lawns and landscapes within 48 hours of one-fourth of an inch or more of rainfall

In all of these cases, excess water can accumulate in catch basins, ground depressions, or cracks in sidewalks and streets, making a perfect place for mosquitoes to lay eggs and develop into biting, and potentially virus-spreading adults. Reducing outdoor water use and dumping and draining all standing water in the yard are simple steps residents can take to eliminate habitats for mosquitoes.
Mosquitoes in California are responsible for transmitting serious viruses such as West Nile and St. Louis encephalitis to people, which can cause debilitating cases of meningitis, encephalitis, and even death. 2017 saw the highest percentage of deaths in California from West Nile virus. There were 553 reported human cases resulting in 44 deaths. It was also the second highest number of deaths in California from the virus in 15 years. Since 2003, 6,583 California residents have been infected with West Nile and over half of them (58%) have developed the neuroinvasive form of the disease. There is no cure for West Nile virus.

To minimize exposure to mosquito bites:

  1. Apply insect repellent containing EPA-registered active ingredients, including DEET, picaradin, oil of lemon eucalyptus, or IR3535 according to label instructions. Repellents keep mosquitoes from biting. DEET can be used safely on infants and children 2 months of age and older.
  2. Dress in long sleeves and pants.
  3. Install screens on windows and doors and keep them in good repair.
  4. Eliminate all sources of standing water on your property, including in flower pots, old tires, and buckets.
  5. Repair leaking faucets and broken sprinklers.
  6. Clean rain gutters clogged with leaves.
  7.  Report neglected swimming pools and day-biting mosquitoes to your local mosquito and vector control agency.

For additional information on mosquitoes and mosquito-borne diseases:

Travelers should refer to the CDC’s Travel Advisories:

To increase awareness and enforce prevention and control programs statewide, the Mosquito and Vector Control Association of California (MVCAC) provides support to more than 65 districts throughout California. As a result, approximately half the land area and 85 percent of California’s population are within the boundaries of a mosquito control program.
MVCAC represents special districts, other subdivisions of local government, and the state of California which are responsible for mosquito and vector control, surveillance of West Nile Virus and other vector-borne diseases, as well as public education programs to help Californians protect themselves from disease. MVCAC advocates safe, effective, and environmentally friendly methods of mosquito and vector control.