The San Mateo County Mosquito and Vector Control District found invasive Aedes aegypti mosquitoes in the unincorporated North Fair Oaks area, the district announced Thursday, Sept. 10.

The district said the risk of disease spreading remains "very low." The species can transmit dengue, chikungunya, Zika and yellow fever, making the detection significant for San Mateo County residents.

This is the second time the invasive mosquito has turned up in the county in recent months, according to the district. The first detection was in the Friendly Acres neighborhood of Redwood City in late July.

District staff will go door to door in North Fair Oaks and nearby areas, checking yards for standing water where the mosquitoes breed, and will set extra traps to gauge how far the population has spread.

"We again need the public's help – this time in North Fair Oaks," District Manager Brian Weber said in the announcement, thanking Friendly Acres neighbors for their earlier cooperation.

They bite during the day.

Aedes aegypti are small, about a quarter-inch long, black and white. They are not native to California but have become established in many counties across the state, according to the district.

Operations Director Casey Stevenson said district staff need only a few minutes per yard to check for water sources. The district urged residents to welcome inspectors onto their properties to help contain the mosquitoes before they spread further.

What residents can do

The district recommends these steps to reduce mosquito breeding:

  • Dump all standing water at least once a week, including in flowerpots, bird baths, old tires, buckets, pet dishes and trash cans.
  • Use EPA-registered insect repellents containing DEET, picaridin, oil of lemon eucalyptus or IR3535.
  • Wear long sleeves, pants, socks and shoes when mosquitoes are active.
  • Make sure window and door screens are in good condition.

The district's services are funded through property taxes and benefit assessments and provided to all San Mateo County residents at no additional charge.

Residents can report biting mosquitoes by calling 650-344-8592 or visiting smcmvcd.org.