Invasive Mosquitoes

If you believe you have seen invasive Aedes mosquitoes in San Mateo County, please call 650-344-8592 or make a service request for insect identification.

Aedes aegypti (Yellow Fever Mosquito)

Mosquito on a white background. The mosquito has an abdomen full of dark red blood. The mosquito is mainly black, with some white stripes on its legs.

Quick facts:

  • Not native to California, but spreading throughout the state.
  • Bites humans during the day.
  • Typically bites on lower legs - earning the name 'ankle biters'
  • Capable of transmitting yellow fever, dengue fever, and chickunguna viruses (the risk of these viruses is low in San Mateo County).
  • In 2013, Aedes aegypti was found in San Mateo County for the first time since being eradicated in 1979.  Through an intensive program, District staff eradicated the species in 2015. Now we are on the look-out again, as this mosquito has been found in Santa Clara County, Santa Cruz County, and Alameda County.

For more information about Aedes aegypti in San Mateo County, visit our Aedes aegypti information page.

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