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The original item was published from 8/4/2023 5:43:06 PM to 10/1/2023 1:00:02 AM.

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Napa County News

Posted on: August 4, 2023

[ARCHIVED] West Nile Virus activity detected in Napa County

NAPA COUNTY, August 4, 2023 - The Napa County Health and Human Services Agency, Public Health Division, and the Napa County Mosquito Abatement District have confirmed the presence of West Nile Virus (WNV) in mosquitos within Napa County. The positive specimen sample was collected on July 19, 2023, in Calistoga. As of August 4, 2023, the Napa County Public Health Division reports no human cases of WNV.

Both humans and animals can contract the virus if bitten by an infected mosquito. Therefore, Napa County Public Health recommends that individuals take preventive measures to avoid mosquito bites, not only in Napa County but also in other regions across California. The virus is transmitted to mosquitos when they feed on infected birds.  

Protect yourself at dawn and dusk

Mosquitoes are most active in the early morning and evening. Avoid being outside at these times. If you are outdoors, wear a long-sleeved shirt and long pants, and use insect repellent.

Drain standing water

Mosquitoes lay their eggs on standing water. Eliminate all sources of standing water on your property and drain empty flowerpots, buckets, barrels, old car tires, rain gutters, and pet bowls. 

Use DEET and other repellents

Insect repellents help keep mosquitoes from biting. Apply an EPA-registered insect repellent containing DEET, picaridin, oil of lemon eucalyptus, IR3535, or para-menthane-diol products per the manufacturer's instructions.

Check doors and windows

Ensure that doors and windows have tight-fitting screens to keep mosquitoes out. Repair or replace screens with tears or holes.

Most people (about 4 in 5) infected with the West Nile virus will not develop any symptoms. About 1 in 5 will develop mild flu-like symptoms, including fever, headache, body aches, nausea, vomiting, and swollen lymph glands. However, about 1 in every 150 people infected with WNV will develop severe neurological disease. In rare cases, WNV infection can be fatal. 

Anyone can be infected with WNV, but people who are 60 years of age or older, those with certain medical conditions (like cancer, diabetes, hypertension, and kidney disease), and people who have received organ transplants are at greater risk of developing severe illness.

Coordinated surveillance work will continue with neighboring Mosquito Abatement District’s and the California Department of Public Health, testing birds and mosquito populations for the presence of this virus.

Residents are encouraged to report dead birds online at or by calling 1-877-WNV­ BIRD (1-877-968-2473). 

For questions about local mosquito surveillance and problems with mosquito control, contact the Napa County Mosquito Abatement District at 707-553-9610.

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