LAKE COUNTY, Calif. — Health and vector control officials said Wednesday that Lake County is experiencing a “concerning uptick” in West Nile virus activity, with the first human cases — including a fatality — reported in five years.
The disease — which hits its peak during the heat of summer, at the same time that mosquito populations increase — is transmitted primarily by the western encephalitis mosquito, known also by its scientific name, Culex tarsalis.
“We find West Nile virus every year in Lake County. Our goal is to 'flatten the mosquito curve' to reduce the risk of people being infected with West Nile virus,” Dr. Jamesina Scott, Ph.D., district manager and research director of the Lake County Vector Control District, said in a joint statement released by her agency and Lake County Public Health.
Of California’s 58 counties, 31 have detected WNV, mainly in mosquitoes, although they’ve also been reported in sentinel chickens, dead birds and horses, according to the state website that tracks the cases.
So far this year, Lake County has had confirmed West Nile virus activity detected in seven mosquito samples and one dead bird.
The first two mosquito samples were collected in early July near Kelseyville and Lakeport. Then, at the start of this month, the Lake County Vector Control District confirmed five more mosquito samples and one dead bird had tested positive for the virus, as Lake County News has reported.
Statewide, the most recent data shows 14 cases in humans, which does not count four confirmed cases in Lake County.
Until this summer, Lake County hadn’t had a confirmed human case of West Nile virus since 2018.
Officials said the first human case reported this year in Lake County became ill during the third week of July. The second probable case that remains under investigation became ill in mid-August.
Both individuals experienced the “neuroinvasive” form of the infection, which can produce symptoms ranging from a form of meningitis to more severe and potentially permanent effects on the nervous system, the county reported.
The third case resulted in a fatality reported earlier this week, officials confirmed. The fourth case was reported to have involved a resident who health officials said contracted the disease out of Lake County.
Since 2004, 14 individuals in Lake County have been diagnosed with West Nile virus, officials said.
Scott said the infection can range from mild, even symptom-free infections, to deadly forms of the disease, with mild forms of the infection often going undetected.
She said less than 1% of cases result in severe illness and these are the most likely to be diagnosed.
An estimated 80% of cases won’t show any signs of infection. Officials said some of those who contract the virus may feel flu-like symptoms including body aches, fever, rash and tiredness.
While many WNV infections can be symptom-free or mild, officials said severe cases can result in encephalitis or meningitis, with potentially permanent effects on the nervous system.
Individuals over the age of 50 and those with conditions like diabetes are at a higher risk for severe forms of the disease.
Symptoms reported for more serious cases include confusion or dizziness, high fever, intense headache, muscle weakness or paralysis, shaking or tremors, and stiff neck.
The Lake County Vector Control District and Public Health Department said the following tips can help protect people from infection:
• Avoid mosquito bites: The most effective way to prevent WNV is to prevent mosquito bites. Use repellents containing DEET, Picaridin, IR3535, or Oil of Lemon Eucalyptus, and wear long-sleeved clothing, especially during dawn and dusk when mosquitoes are most active.
• Eliminate standing water: Remove any stagnant water around your property. Mosquitoes need water for breeding. For larger water sources, like unmaintained swimming pools, the Vector Control District provides free mosquito-eating fish.
• Report concerns: Residents should report dead birds, especially crows, ravens, and scrub-jays, as they can be indicators of WNV activity. Report them to the state's toll-free hotline at 1-877-968-2473 (1-877-WNV-BIRD) or online.
• Don’t leave swimming pools or large standing water areas neglected, as they can create breeding areas for mosquitoes. The Lake County Vector Control District offers mosquitofish for standing water; call the district at 707-263-4770 to request fish or submit a request online.
Email Elizabeth Larson at This email address is being protected from spambots. You need JavaScript enabled to view it.. Follow her on Twitter, @ERLarson, or Lake County News, @LakeCoNews.
Health officials report increase in West Nile virus activity
- Elizabeth Larson
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