A Culex quinquefasciatus mosquito. Photo by James Gathany, USCDCP on Pixnio

The Fresno County Department of Public Health announced Tuesday the  first confirmed case of St. Louis Encephalitis virus infection for 2023.

St. Louis Encephalitis virus (SLEV) is a bird-borne illness carried by mosquitoes that bite infected birds.

In humans, symptoms can include fever, headache, dizziness, nausea and weakness that progressively get worse over a period of several days to a week. Most infections result in mild cases with few or no symptoms, but more serious symptoms include stiff neck, confusion, disorientation, dizziness, tremors and unsteadiness.

Additionally, SLEV can produce inflammation of the brain, potentially leading to comas in severe cases.

There are currently no vaccines or medicines to prevent or treat SLEV.

“This positive case is a strong reminder that we need to stay vigilant as mosquitoes may continue to cause several severe illnesses, including West Nile Virus (WNV) infection, which require hospitalization and intensive care,” said Fresno County Interim Health Officer Dr. Rais Vohra.

The department recommends residents contact their local mosquito control district regarding issues with mosquitoes, as well as to report standing water or neglected swimming pools. Neglected pools are a leading source of mosquito production in urban and suburban areas.

The department also recommends residents practice the “three Ds”:

Deter – Use insect repellents containing DEET, picaridin, oil of lemon eucalyptus or IR3535. Repellents prevent mosquito bites. Repellents should not be used on children under two months.

Dawn and Dusk – Mosquitoes are most active in the early mornings and evenings. It is recommended to wear proper clothing and repellent especially during these times. Additionally, ensure doors and windows have tight-fitting screens to keep mosquitoes out.

Drain – Eliminate sources of standing water. Be sure to check flowerpots, old car tires, buckets and other containers. Ensure windows and drains are covered by screens. Swimming pools should also be properly maintained to deter mosquito reproduction.

Residents are encouraged to report dead birds by visiting https://westnile.ca.gov/ or by calling 1-877-WNV-BIRD (968-2473).

Additional information can be found at the websites listed below:

Centers for Disease Control and Prevention: http://www.cdc.gov/sle/index.html. 

California Department of Public Health: https://bit.ly/39nevb7

California WNV Website: https://westnile.ca.gov/

California SLEV Website: https://westnile.ca.gov/sle.php.

Fresno County Mosquito Control District: https://fresnocountymosquito.org/