The first invasive mosquito species has been found in Contra Costa County, according to the Contra Costa Mosquito & Vector Control District.

The species Aedes aegypti was discovered in Martinez. The district is conducting surveillance and treatment in the area they were found, hoping to eliminate them before they spread. The district said in a statement last Friday, "They are known to be very difficult to eradicate."

"These mosquitoes are very aggressive day-biters that can transmit the causative agents of Zika, dengue, chikungunya, and yellow fever. They can hide among vegetation and debris which makes them very challenging to find and eliminate," said Paula Macedo, the general manager of the Contra Costa Mosquito & Vector Control District.

"As we take our responsibility of protecting public health very seriously, we are setting additional traps, and going door-to-door in an effort to find and control these invasive mosquitoes and prevent them from becoming established in the county," Macedo said.

Aedes aegypti aren't native to California but can be found around the world in tropical and subtropical areas. They're common in the southeastern United States and Arizona. They were discovered more than a decade ago in Southern California and, over the years, have been found from San Diego to Shasta counties. In 2019, Aedes aegypti were discovered in San Joaquin, Sacramento, and Yolo counties.

The mosquitoes are very small -- about 1/4 inch -- with black bodies and white stripes. Females can lay eggs that remain dormant up to six months before being exposed to water, in which they can develop from egg to adult in less than a week. They're often introduced through travel, particularly as people move from area to area and may unknowingly transport them in potted plants or other outdoor items.

The district asks residents to take action to reduce the risk of these new mosquitoes. Recommendations include getting rid of standing water, scrubbing bird baths, containers, outdoor pet dishes, garden pots for plants, and anything else that can hold water outdoors. People can report any day-biting mosquitoes by calling 925-685-9301 or going to https://contracosta.leateamapps.com/#/public/servicerequest.