Invasive 'yellow fever mosquito' known to carry disease found in North Concord

CONCORD, Calif. (KGO) -- An invasive, non-native mosquito known to carry diseases and not seen in Contra Costa County in two years has been found in North Concord.

Inspectors from the Contra Costa Mosquito & Vector Control District are testing standing water in areas in northern Concord. They are looking for eggs and larvae of Aedes Aegypti mosquitos - a potentially dangerous bug.

"You see a mosquito biting you, you swat it on your arm. This is not that mosquito," explains Nola Woods, with the Contra Costa Mosquito & Vector Control District. "Its common name is the yellow fever mosquito. So, it's a really dangerous mosquito and we found one."

"We found this mosquito in one of our routine West Nile virus surveillance traps, which shows that our surveillance system is working," said Steve Schutz, the district's scientific programs manager. "Additional trapping and inspections are being carried out in the area to determine the extent of the infestation and prevent it from spreading."

Woods says this type of mosquito can carry dengue fever, chikungunya and the Zika virus. The zika virus can cause birth defects.

"It raises the alarm because where there is one, there is likely more," says Woods.

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So far only one mosquito has been found, which suggests they are not here in high frequency. But two years ago, a large number of yellow fever mosquitos were found in Martinez, which have since been eradicated.

One challenge is that this mosquito lays sticky eggs, often in warm water, that easily attach to surfaces or planters.

"So when you dump out water, they are not gone. You literally have to scrub them off," says Woods. "That adds to the risk that they can be on something, maybe an imported plant, or something like that, without you knowing it and bring it to a new community. And the water activates them."

This type of mosquito is not native to the Bay Area and were first spotted in Southern California 10 years ago. They are now established in 24 counties across the state.

Woods says these mosquitos fly low and usually bite below the knee. The district said in a statement that the mosquito is very stealth-like, flying low to the ground, and has been called an "ankle biter."

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Doctor Peter Chin-Hong is an infectious disease specialist at UCSF. He says this should not trigger a panic, but should have people on alert for diseases not typically found in the Bay Area.

"It reflects the reality of climate change, it reflects the reality of diseases being spread in areas that don't normally see it," says Dr, Chin-Hong.

He says a bite can cause flu-like symptoms, headaches, muscle cramps and fatigue. Given that a yellow fever mosquito has been found, he suggests if you get a bite and show symptoms, it's best to get medical attention.

"People wouldn't know what kind of mosquito bites them. So, in general if you get a mosquito bite.. with flu-like symptom, I think having a clinician examine you, do additional testing, is important," says Dr. Chin-Hong.

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He adds wearing long-sleeves and pants, using insect repellents and emptying standing water in-and-around your house can help protect against mosquito bites.

"And avoiding dusk and dawn in general. That's the time when mosquitoes generally feed the most," shares Chin-Hong.

To reduce the risk of mosquito bites, residents are encouraged to use an EPA-registered insect repellent containing active ingredients like DEET, picaridin, the repellent version of oil of lemon eucalyptus, or IR3535.

People should also check window screens to make sure they fit properly without any gaps or rips in the screen.

The district will continue to spray and test, hoping to prevent these mosquitos from establishing a presence in Contra Costa County.

"We will continue to look and continue to mitigate that issue because they are not mosquitos you want in your community," says Woods.

County residents who experience day-biting mosquitoes should contact the district and request mosquito service by calling (925) 685-9301 or by visiting this website.

Signing up for district notifications allows county residents to receive information on West Nile virus activity and adult mosquito control operations in real time. Subscribe here.

Bay City News contributed to this report