More Mosquitoes Test Positive For West Nile Virus In Contra Costa

CONTRA COSTA COUNTY, CA — More mosquitoes have tested positive for West Nile virus in Contra Costa County, authorities said Friday.

The mosquitoes were collected from a trap in an agricultural area east of Brentwood, according to a news release from the Contra Costa Mosquito & Vector Control District.

A previous group of mosquitoes that tested positive this year for WNV was found in Oakley.

WNV comes from certain birds, mostly crows and jays; mosquitoes become infected after biting an infected bird.

The news of more WNV-infected mosquitoes comes a week after the District announced the discovery of an invasive mosquito species in Contra Costa County. Aedes aegypti mosquitoes can transmit the causative agents of Zika virus, Dengue fever, Chikungunya virus, and Yellow fever, which is why the district asked all Contra Costa County residents to "tip, toss and take action to reduce the risk of mosquitoes" by doing the following:

• Tip over any size outdoor container to toss out any amount of standing water
• After tossing out the water, take action by scrubbing the inside of any outdoor container because Aedes aegypti eggs can stick to bird baths, buckets, outdoor pet dishes, garden pots for plants, and anything else that can hold water outdoors.
• And report mosquito issues by calling 925-685-9301 or online.

"The source of mosquitoes is often right in our own backyards," said Steve Schutz of the Contra Costa Mosquito & Vector Control District. "That’s why we’ve always provided residential inspections, and now that we've discovered invasive Aedes aegypti, we are going door-to-door in the affected area to conduct inspections and treatment if necessary, in an effort to prevent this mosquito from spreading across Contra Costa County."

Backyard inspections are critically important when it comes to Aedes aegypti because they are tiny mosquitoes that are well adapted to living around our homes, depositing eggs in almost any container that can hold water, Schutz said.

"The key to controlling them is to find, drain these containers and keep them dry because a single missed source could re-infest an entire neighborhood," he said.

In addition to dumping out and scrubbing outdoor sources of standing water, authorities recommend residents use EPA-registered insect repellents when mosquitoes are present. The most effective repellents contain one of the following active ingredients: DEET, Picaridin or Oil of Lemon Eucalyptus.

Contra Costa County residents can report dead birds by phone at 877-WNV-BIRD (968-2473) or online. County residents can also request mosquito service for residential property by calling 925-685-9301 or online.

Since 2005, 75 people in Contra Costa County have been diagnosed with West Nile virus. In 2006, two people died from the disease in the county. For human West Nile virus case information, visit the California Department of Public Health Vector-Borne Disease Section online.

Aedes aegpyti mosquitoes become infected with Zika, Dengue, Chikungunya, or Yellow fever after biting an infected person; as of Friday, authorities said there were no reports of local transmission within California.

Any cases of these diseases have been acquired due to travel; however, the more widespread these mosquitoes become, there is an increased risk of potential local transmission. That is why the district said it was working to control these mosquitoes in Contra Costa County. Residents who are being bitten by day-biting mosquitoes should contact the district by calling 925-685-9301 or online.