Stanislaus County Public Health officials are reporting a significant increase in West Nile Virus (WNV) cases for the 2023 year compared with recent previous years. WNV is primarily transmitted to humans through the bite of infected mosquitoes. As of Sept. 15, 2023, a total of 28 WNV human cases, including one death, have been reported in Stanislaus County residents compared to 15 WNV cases for the entire 2022 season. Nineteen of the 2023 WNV cases reported so far have been neuroinvasive WNV, where those infected developed neurological illnesses.
While most people infected with WNV are asymptomatic or have only mild illness, those who develop neuroinvasive WNV can have serious complications, such as encephalitis or meningitis. This can lead to long‐term disability or death. Some populations, such as older adults, people with diabetes, and people with weakened immune systems, are more likely to develop severe illness when infected with WNV.
Increased mosquito activity this year was anticipated with the heavy rains over the previous winter season. California as a whole has also seen an increase in WNV cases. As of Sept. 15, there have been 124 human cases of WNV reported statewide compared to 51 cases as of this date in 2022.
“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.
Public Health officials emphasize the importance of taking proactive measures to prevent mosquito bites and helping to keep mosquito numbers in check to reduce the risk of further disease transmission in the community.
Dr. Thea Papasozomenos, Stanislaus County Public Health officer, stressed the importance of community awareness and engagement: “Unfortunately, there is no human vaccine and no specific treatment for West Nile Virus. 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.”
Humans and horses are dead‐end hosts for WNV because virus levels do not typically get high enough to lead to further transmission, with a mosquito biting an infected individual. Infection in birds can lead to further transmission because the virus levels get high in them to allow further spread.
The best way to control the spread is by controlling the mosquito population, utilizing the ‘four D’s’ of prevention.
DRAIN all sources of standing water around homes and properties to prevent mosquito breeding. Regularly empty flowerpots, bird baths, gutters, and other containers that collect water.
DRESS in long sleeves, long pants, socks, and shoes outdoors to minimize exposure to mosquito bites, especially during dawn and dusk when mosquitoes are most active.
DEFEND with an Environmental Protection Agency (EPA)‐registered insect repellent that contains ingredients like DEET, picaridin, or oil of lemon eucalyptus to protect exposed skin from mosquito bites.
DUSK and DAWN: Minimize outdoor activities during peak mosquito activity times, typically during dawn and dusk.
Birds serve as the natural hosts of WNV. Residents who come across dead birds, particularly crows, jays, ravens, or birds of prey, are encouraged to report them to California West Nile Virus dead bird call center at (877) WNV‐BIRD (968‐2473) or westnile.ca.gov/report.
Also, report neglected swimming pools to your local mosquito abatement district.
For up‐to‐date information and resources related to West Nile Virus and the ongoing efforts to prevent its spread, visit westnile.ca.gov/faq.