A Stanislaus County woman has become the first person this year in the county to be diagnosed with St. Louis encephalitis virus, according to the Stanislaus County Health Services Agency.

The woman’s name and hometown were not released. She is in her 50s. She had neurologic symptoms and was tested in September; confirmatory testing was performed by the California Department of Public Health and recently released by the SCHSA. 

As of the last state surveillance report of Nov. 5, St. Louis encephalitis virus has been detected in mosquitoes in eight California counties. The Stanislaus County woman is the one person in California testing positive for SLEV in 2021.

SLEV is transmitted to humans by the bite of an infected mosquito. SLEV was detected in mosquitoes in Stanislaus County in September of this year. Most people infected with SLEV have no apparent illness. Initial symptoms of those who become ill include fever, headache, nausea, vomiting, and tiredness. Severe neuroinvasive disease (often involving encephalitis, an inflammation of the brain) occurs more commonly in older adults. Like West Nile, there is no vaccine or specific treatment for SLEV infection. 

Stanislaus County residents can protect themselves and their families by following these simple steps: 

DEET – Apply insect repellent containing DEET, picaridin, oil of lemon eucalyptus or IR 3535 according to label instructions to keep mosquitoes from biting you. Apply repellents only to exposed skin and/or clothing. DEET can be used safely on infants and children two months of age and older. Permethrin is a repellent/insecticide that can be applied to clothing and will provide excellent protection through multiple washes. You can treat clothing yourself (always follow the directions on the package!) or purchase pre-treated clothing. For best protection it is still necessary to apply other repellent to exposed skin. 

DAWN AND DUSK – Mosquitoes that carry SLEV and West Nile virus tend to bite in the early morning and evening, so it is important to wear repellent at this time. Make sure that your doors and windows have tight-fitting screens to keep out mosquitoes. Repair or replace screens with tears or holes. 

DRESS – Wear clothing that reduces the risk of skin exposure to mosquito bites (i.e., socks, long pants, and long-sleeved shirts). 

DRAIN – Mosquitoes lay their eggs on standing water. Eliminate all sources of standing water on your property, including flowerpots, old car tires, rain gutters and pet bowls. If you have a pond, use mosquito fish or commercially available products to eliminate mosquito larvae. 

Change the water in pet dishes and replace the water in bird baths weekly. Drill holes in tire swings so water drains out. Empty children’s wading pools and store on their side after use. 

Neglected swimming pools are also prime place for mosquito breeding. 

The Turlock Mosquito Abatement District is available to help with neglected pools in the prevention of mosquito development. To request District service call 209-634-1234 or visit the website at www.turlockmosquito.org