San Andreas, CA—A third Mother Lode County has detected the deadly West Nile Virus, as two sentinel chickens in the Copperopolis area tested positive.
Mosquitoes carry the virus and spread it when they bite. Calaveras County Public Health officials relayed that this is the first sign of the virus in Calaveras County this year and no human cases have been reported in the county. However, in neighboring Tuolumne County, as we reported at the end of August, health officials alerted the public to a human infection, stressing that August and September are the peak times for the virus.
Calaveras Public Health shared that blood samples were taken from ten sentinel chickens in the Copperopolis flock on September 17, 2026. Sentinel chickens are kept outdoors and tested on a regular schedule to watch for viruses spread by mosquitoes. The samples were tested on September 25, with two of the ten samples testing positive. The county was notified of the results today, September 29th.
While chickens cannot spread the virus to humans, a positive result means mosquitoes carrying West Nile virus are active in the area. Mosquitoes stay active until the weather turns cold, so health officials ask all those in and around Copperopolis to take steps now to avoid mosquito bites.
“We care deeply about the health and well-being of our community, which is why we monitor local mosquito activity so closely,” said Dr. René Ramirez, County Health Officer. “While there are no human cases in our county, the virus is present in local mosquitoes. We encourage everyone to take simple, everyday precautions—like using EPA-registered insect repellent and clearing standing water around the home—so we can all stay safe and healthy this season.”
These latest results may not show up on the state’s West Nile virus website right away, as it has been an active virus season. Along with the Tuolumne County human case, San Joaquin County has reported five, and Stanislaus County six. Additionally, two horses in Amador County have also tested positive.
Health officials provided these three easy ways to protect yourself:
- Use bug spray. Pick one with DEET, picaridin, oil of lemon eucalyptus (do not use on children under 3 years old), or IR3535, and follow the directions on the label. Used this way, DEET is safe for children 2 months and older and for women who are pregnant or breastfeeding. Stronger sprays last longer: 10% DEET protects for about 2 hours, and about 25% DEET protects for about 5 hours. Sprays with more than 50% DEET do not work any better. Put more on if you stay outside longer than your spray lasts.
- Cover up at dawn and dusk. Mosquitoes bite most in the early morning and the evening. Wear loose, long-sleeved shirts and long pants. Keep screens on your doors and windows and fix any rips or holes.
- Dump standing water. Mosquitoes lay their eggs in water that sits still. Empty flowerpots, buckets, old tires, pool covers, pet bowls, and toys. Change your pet’s water every day and bird bath water every week. A young mosquito can grow into an adult in only seven days.
“Don’t forget about our pets! Pet bug spray formulated just for animals is available at pet stores or check with your veterinarian for other options,” Environmental Management Agency Administrator Lisa Medina stated, adding, “Horses can also get very sick from West Nile virus. Horse owners should speak with their veterinarian about vaccinating their horses.”
For protections, symptoms, and why it is important to report dead birds to wildlife officials, click here.
