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West Nile Virus activity on the rise
WNV activity map
On this map from the Turlock Mosquito Control District, the yellow shaded areas indicate where West Nile Virus activity has been found in mosquitos. The blue shaded areas are where aerial spraying is scheduled.

A mosquito bite this time of year could bring something far more serious than an irritating itch.

The Stanislaus County Health Services Agency is reporting a “significant increase in West Nile Virus (WNV) cases for the 2023 year compared with recent previous years.”

As of Friday, Stanislaus County has recorded 28 West Nile Virus cases, including one death. There were 15 cases in Stanislaus County during the entire West Nile Virus season in 2022, according to the SCHSA.

Not only have there been more cases this year, there has been more serious illnesses from the neuroinvasive form of the virus. Nineteen of those infected in the county have developed neurological illnesses, the SCHSA reported.

The state also is reporting increased infections of the virus this year. As of Friday, 124 human cases of WNV had been reported compared to 51 cases as of this date in 2022.

The increased mosquito activity is a result of the increased rains during winter and spring.

"The early arrival of mosquitoes this season with the heavy winter rains allowed West Nile Virus infection to get started earlier this season, leading to a heavy disease burden," said David Heft, General Manager for Turlock Mosquito Abatement District.   

Mosquitoes become infected with West Nile Virus when they feed on infected birds. Infected mosquitoes can then spread West Nile Virus to humans and other animals when they bite, according to the Centers for Disease Control.

Approximately 1 in 5 people who are infected with West Nile virus will develop symptoms such as fever, headache, body aches, joint pains, vomiting, diarrhea, or rash. Less than 1 percent will develop a serious neurologic illness such as encephalitis or meningitis (inflammation of the brain or surrounding tissues). About 10 percent of people who develop neurologic infection due to West Nile virus will die, according to the CDC. People over 50 years of age and those with certain medical conditions, such as cancer, diabetes, hypertension, kidney disease, and organ transplants, are at greater risk for serious illness.

There are no medications to treat or vaccines to prevent West Nile Virus infection. People with milder illnesses typically recover on their own, although symptoms may last for several weeks or months. In the neuroinvasive forms, patients can suffer severe and sometimes long-term symptoms.

"Unfortunately, there is no human vaccine and no specific treatment for West Nile Virus,” said Dr. Thea Papasozomenos, Stanislaus County Public Health officer. “With the high amount of West Nile Virus activity we are seeing this year, it is important for people, especially those most at‐risk for serious illness, to take steps to protect themselves and their families from mosquito bites."

Mosquitoes like to breed in stagnant water, preferring weedy areas that provide cover. The lagoons at dairy farms make for perfect breeding grounds, but so do flooded fields, uncared for swimming pools, urban catch basins, overwatered lawns, and pretty much anything that holds water and allows it to stagnate.

The local mosquito abatement districts will continue with their treatment and surveillance programs by identifying mosquito breeding sources and mosquito borne disease activity. They will perform treatments according to their surveillance results. The Districts would like to remind residents that they can help by taking the following precautions:

• Dump or drain standing water. These are places mosquitoes like to lay their eggs.

• Defend yourself against mosquitoes by using repellants containing DEET, Picaridin or Oil of Lemon Eucalyptus.

• Avoid being outdoors at dusk and dawn. These are the times when WNV carrying mosquitoes are generally most active.

 •Report neglected swimming pools to your local mosquito abatement district.

• Use tight fitting door and window screens to keep mosquitoes from entering your home.

• Contact your veterinarian for information on vaccinating equine against WNV.

For additional information or to request service, Turlock residents should contact the Turlock Mosquito Abatement District at (209) 634-1234 or (

Reporting and testing of dead birds are important steps in preventing West Nile Virus. A confirmed case of the virus in dead birds or mosquito samples helps to identify areas that need treatment to reduce mosquito activity. To report a dead bird, call the California State hotline at 1-877-WNV-BIRD or report it online at Birds of particular interest are crows, ravens, magpies, jays and raptors (hawk or eagle).