Placer County detects first West Nile Virus-positive mosquito samples of 2026
West Nile Virus positive mosquitoes have been found in west Placer County, the Placer Mosquito and Vector Control district announced Wednesday.
The mosquitoes, collected from an agricultural area near Sheridan and west of Lincoln, and from a residential area near Morgan Creek, were the first samples to test positive for West Nile Virus in Placer County this year. The announcement followed the report of the first human infection of the mosquito-borne illness in Sacramento County — and the second in California overall — last Thursday.
“As we’ve seen in past years, we predict more West Nile virus activity following this initial detection,” Joel Buettner, the district’s general manager, said in a statement.
Last year, district officials reported the first mosquito sample to test positive for the disease on Jun. 18, 2025, and the first human case of the infection on Aug. 29, 2025. There were six human cases of West Nile Virus in Placer County overall by the end of the year, including one fatal infection reported in October.
While neighboring Yuba and Sutter counties have reported no West Nile Virus activity this year, the Sacramento-Yolo Mosquito & Vector Control District has witnessed increased West Nile Virus activity in Sacramento County since the beginning of mosquito season, which typically spans from May through October.
After the first West Nile Virus positive mosquito sample was detected in Sacramento County on May 20, 40 dead birds and 24 additional mosquito samples have tested positive for the disease in Sacramento and Yolo counties, with Yolo County reporting its first positive mosquito sample on Monday.
The U.S. Center for Disease Control and Prevention also warned that West Nile Virus is at its highest nationwide since 2004. At least 48 cases of the disease had been reported as of June 30 — including 38 with severe symptoms — compared to the average 10 typically reported to the CDC by the end of June.
Attributing the surge to “early circulation of the virus,” a spokesperson for the organization added that 23 states have reported West Nile Virus activity this year — the highest number in the past decade.
Placer Mosquito District officials encouraged residents to take preventative measures to protect themselves from mosquito bites, citing the lack of an effective cure to remedy the disease and its potentially serious symptoms.
According to the CDC, while most West Nile Virus infections are asymptomatic, approximately 20% of those infected with the disease develop mild flu-like symptoms, including fever, headache, body aches, vomiting, diarrhea, rash and joint pains.
While those with mild symptoms tend to recover completely — with some fatigue and weakness potentially enduring for months — in some severe cases, the disease can affect the central nervous system, causing encephalitis or meningitis that requires hospitalization.
Immunocompromised, elderly and individuals with chronic medical conditions are at particularly high risk of developing severe illnesses caused by a West Nile Virus infection. Approximately 10% of patients that experience severe neuroinvasive symptoms die as a result of the disease, according to the CDC.
How can I protect myself from mosquito bites?
The Sacramento-Yolo Mosquito & Vector Control District recommends the “seven Ds of mosquito prevention” to limit the risk of mosquito bites:
- Drain any standing water that may serve as mosquito breeding sites.
- Dawn and dusk are when mosquitoes are most active, and times to avoid being outdoors.
- Dress appropriately by wearing long sleeves and pants when outdoors.
- Defend yourself from mosquitoes by using and correctly applying effective insect repellent, like DEET, Picaridin, or Oil of Lemon Eucalyptus.
- Door and window screens should be kept in good working condition to prevent mosquitoes from entering your home.
- District personnel are who to go to if you face mosquito problems.
Placer County residents can report mosquito problems placermosquito.org or via 916-380-5444. Sacramento and Yolo County residents can contact officials at 800-429-1022 or visit FightTheBite.net.
