Skip to main content
Vector Control District
Vector Control District

Wide Area Larvicide Spraying Treatments for Invasive Aedes Aegypti Mosquito

For additional information on scheduled wide area larvicide spraying treatments for the invasive Aedes aegypti mosquito, please click here.

Press Release - Nov. 14, 2024

FOR IMMEDIATE RELEASE
Nov. 14, 2024

Invasive Mosquitoes Detected in Fourth Location in San Jose

The County of Santa Clara Vector Control District has now detected the invasive Aedes aegypti mosquito in a total of six locations in Santa Clara County, highlighting the urgent need for ongoing community action

SANTA CLARA COUNTY, CALIF. — The invasive Aedes aegypti mosquito has been detected in a fourth location in San Jose, continuing to gain ground in Santa Clara County despite aggressive attempts to eliminate it. The invasive species is able to transmit diseases such as Zika and yellow fever.

The day-biting mosquito is now present in a total of six locations in Santa Clara County. 

The County of Santa Clara Vector Control District made its latest discovery in an area of San Jose near Cortez Avenue and Orlando Drive. The recent detection came as the district continues its effort to eliminate the day-biting mosquitoes from three other areas of San Jose as well as neighborhoods in the cities of Gilroy and Santa Clara. The County aims to prevent the invasive mosquito from establishing a permanent population.

The Vector Control District, which has conducted extensive outreach to affected residents and businesses in recent months, will hold a community meeting on Monday, Nov. 18, in San Jose to answer questions and discuss the district’s plan to treat the area near Cortez Avenue and Orlando Drive. More information on the meeting is available below.

The new detections underscore the urgent need for the public to help detect and eliminate the day-biting mosquitoes. The County asks businesses and residents to remove any sources of standing water on their properties and clean items like outdoor pet dishes that may contain mosquito eggs, as this is the most effective way for community members to help.

“The threat posed by Aedes aegypti is growing, and we need everyone to pitch in now to prevent this day-biting mosquito from becoming established in Santa Clara County,” said Edgar Nolasco, director of the County of Santa Clara Consumer and Environmental Protection Agency. “In the interest of public health, we need businesses and residents to check their properties for sources of standing water and remove them. And we need the people who live in areas where this invasive mosquito has been found to work together with district staff and allow them to inspect their properties.”

The day-biting mosquito has the potential to transmit diseases that are not endemic to the United States, including dengue, chikungunya, Zika and yellow fever.

The invasive mosquito has now been found in six locations:

  • South San José: 44 mosquitoes 
  • Santa Clara: 172 mosquitoes 
  • Gilroy: six mosquitoes 
  • East San José: 151 mosquitoes 
  • San José (near Oak Hill Funeral Home & Memorial Park): two mosquitoes 
  • San José (near Cortez Avenue and Orlando Drive): 10 mosquitoes 

The Vector Control District has increased its outreach and education this year in response to detections throughout the county, which has led to more vigilance and reporting by members of the community. Mosquito activity is increasing with climate change, and Aedes aegypti has now been detected, though it is not yet established, in four Bay Area counties.

Aedes aegypti is established in 19 counties throughout the state, mostly in the Central Valley and Southern California. The Los Angeles County Department of Public Health has now reported 12 cases of locally acquired dengue in 2024.

If the day-biting mosquito establishes a permanent population in Santa Clara County, it will not only threaten public health but also affect our quality of life, as these mosquitoes are highly aggressive and active during the day, unlike native mosquito populations, which are most active in the morning and evening, when temperatures are cool.

District staff are carrying out a thorough eradication plan in the areas where the day-biting mosquito has been found, trapping adult mosquitoes, inspecting properties to find mosquito larvae and habitat (i.e., standing water), and treating any larvae they find with pesticide. 

The day-biting mosquito is tenacious, however, and difficult to exterminate. These mosquitoes need very little water to lay their eggs, which can last for more than a year in dry conditions, and they often lay them in hard-to-reach places.

Aedes aegypti bites at any time of day. The invasive mosquitoes are “container breeders,” preferring to lay their eggs just above the water line in small, artificial sources of water such as buckets, pet dishes, fountains and bird baths, plant pots and saucers, and old tires. 

The invasive species is about a quarter-inch in size with black and white stripes on its back and legs. It feeds almost exclusively on humans and does not fly long distances, venturing fewer than 500 feet from where it hatches. 

The public plays a critical role in controlling the spread of this mosquito. It's important for residents in Santa Clara County to do the following:

  • Allow district staff to access their properties to do the important job of checking for mosquitoes and treating them as needed. 
  • Report day-biting mosquitoes immediately to the Vector Control District at (408) 918-4770 or [email protected]. (Residents can send photographs of mosquitoes with black and white stripes to the same email address.)
  • Dump out any containers that are filled with water and clean them by scrubbing them with hot, soapy water or undiluted bleach.

Residents throughout the county should look around their properties and dump out even the smallest amount of standing water. Cleaning and scrubbing bird baths, pet dishes and other containers can remove any lingering Aedes aegypti eggs, which are about half a millimeter in size and look to the naked eye like tiny bits of dirt. Scrub these items with soap or bleach and then leave them to dry for at least 24 hours. Only rinse these items when ready to use them again.

The district will hold a community meeting in San Jose next week at the time and location below:

Anthony Dorsa Elementary School – Multipurpose Room
1290 Bal Harbor Way, San Jose
Monday, Nov. 18, at 6:30 p.m.

The district will soon begin treating the area surrounding Cortez Avenue and Orlando Drive to eradicate the aggressive species of mosquito. The treatment will include wide area larvicide spraying, which is done with the use of truck-mounted equipment and will be conducted in a series of treatments. Control methods may be escalated to include adult-mosquito-control treatments if necessary.

Vector control staff who enter residential or commercial properties are not authorized to do anything besides check for mosquitoes and provide mosquito control as needed. The inspections are provided at no cost.

To protect yourself from mosquito bites:
  • Apply insect repellents containing EPA-registered ingredients such as DEET, picaridin, IR3535 or oil of lemon eucalyptus, always following label instructions.
  • Wear long-sleeve shirts, pants, socks and shoes when mosquitoes are most active. 
  • Make sure your window and door screens are in good condition. 
Residents throughout Santa Clara County should also:
  • Properly screen rain barrels, cisterns and irrigation drains to prevent mosquito access.
  • Fix leaky water faucets and broken sprinkler heads and avoid overwatering lawns and plants.
  • Ensure window and door screens are in good condition with no holes or tears and are tight-fitting.
  • Make sure the water level of swimming pools is adequate for proper circulation and filtration.

To reduce the population of Aedes aegypti, the district uses pesticides that are approved by the Federal and State environmental protection agencies and are widely used by vector control agencies throughout California. 

The California Department of Public Health tests the mosquitoes the district traps for any viruses. To date, none of the viruses that potentially can be transmitted by the invasive mosquitoes have been transmitted in Santa Clara County. 

The County Public Health Department monitors for the occurrence of viruses transmitted by Aedes aegypti and any unusual diseases in partnership with local medical providers and laboratories, who are required to report certain diseases and conditions to Public Health.

If you are sick with fever, headache and joint or muscle pain after returning from an area where dengue, chikungunya, yellow fever or Zika occurs, contact your doctor, and stay indoors as much as possible to avoid mosquito bites and help prevent the possible spread of the virus. 

For more information or frequently asked questions on Aedes aegypti, visit the district’s invasive mosquitoes webpage or the California Department of Public Health’s Aedes aegypti and Aedes albopictus webpage.
 

ABOUT THE COUNTY OF SANTA CLARA, CALIFORNIA 

The County of Santa Clara government serves a diverse, multicultural population of 1.9 million residents in Santa Clara County, making it more populous than 14 states in the United States. The County provides essential services to its residents, including public health protection, environmental stewardship, medical services through the County of Santa Clara Health System, child and adult protection services, homelessness prevention and solutions, roads, park services, libraries, emergency response to disasters, protection of minority communities and those under threat, access to a fair criminal justice system, and many other public benefits.

Visit the County of Santa Clara at: www.santaclaracounty.gov

Like us on Facebook: Facebook.com/County.of.Santa.Clara

Follow us on X: X.com/sccgov