The San Mateo County Mosquito and Vector Control District confirmed Monday, July 27, that invasive Aedes aegypti mosquitoes have been found in Redwood City's Friendly Acres neighborhood, marking the first detection of the disease-capable species in the county since it was eradicated from Menlo Park more than a decade ago.
District crews are now going door to door in Friendly Acres and surrounding areas, searching for standing water where the mosquitoes breed and deploying additional traps to gauge how far the insects have spread.
"We need the public's help to stop this mosquito," District Manager Brian Weber said in the district's announcement. "Our goal is to control and eliminate invasive Aedes aegypti mosquitoes from San Mateo County."
Why it matters countywide
Aedes aegypti can transmit dengue, chikungunya, Zika, and yellow fever. The district said the current risk of disease transmission in San Mateo County is very low, but the species poses a long-term public health concern because it bites aggressively during the day, unlike native mosquitoes that are most active at dusk and dawn.
The quarter-inch black-and-white insects are not native to California. They first arrived in the state in 2013 and have since become established in many California counties. The district serves all 20 cities in San Mateo County.
As we reported July 22, warming summers have been accelerating mosquito breeding cycles across San Mateo County. The confirmed presence of an invasive species adds urgency to those seasonal warnings.
County has beaten this mosquito before
The last time Aedes aegypti was confirmed in San Mateo County was in Menlo Park between 2013 and 2015. The district successfully eradicated it then with resident cooperation.
Operations Director Casey Stevenson said that earlier success depended on residents dumping standing water, reporting biting mosquitoes, and allowing inspectors onto their properties.
What residents should do
Communications Director Rachel Curtis-Robles said even a bottle cap's worth of water can produce mosquitoes, and urged residents to check around their homes and dump water at least once a week.
The district is asking all San Mateo County residents to take these steps:
- Dump standing water at least once a week. Check flowerpot saucers, bird baths, pet dishes, old tires, buckets, and trash cans.
- Apply EPA-registered repellent containing DEET, picaridin, oil of lemon eucalyptus, or IR3535 when outdoors.
- Wear long sleeves, pants, socks, and shoes when mosquitoes are active.
- Check window and door screens for holes or gaps.
- Report biting mosquitoes to the district at 650-344-8592 or at www.smcmvcd.org.
District inspections and trapping in the Friendly Acres area are ongoing, though no completion date has been announced. Residents who spot small black-and-white mosquitoes biting during the day can call 650-344-8592 to request a free property inspection.
