San Joaquin County Public Health Services has confirmed a West Nile Virus (WNV) infection in the county related to an older adult male patient. This is the first confirmed human case in San Joaquin County for 2025, the 14th county to report a case, and the 61st human case in California for this year.
This mosquito-borne disease was first detected in California in 2003 and now is routinely detected throughout the state. It is the leading cause of mosquito-borne disease in the continental United States.
“Mosquito bite prevention is always the best course of action, and we encourage the residents of our county to protect themselves by wearing EPA-approved repellents and following CDPH (California Department of Public Health) vector protection guidelines,” said Dr. Maggie Park, San Joaquin County Public Health Officer.
Be aware of symptoms of serious infection such as fever, severe headaches, stiff neck, disorientation, or confusion. Seek medical attention if you believe you have been bitten and these symptoms are present.
Although about 80 percent of those infected will not present symptoms, about one percent of those infected will develop serious symptoms. The most vulnerable populations are those with weakened immune systems, those over 60, and people with diabetes or kidney disease.
The most effective method for preventing WNV infection is to avoid being bitten by mosquitoes. Take these three precautionary measures:
* Drain and dump out any standing water where mosquitos lay eggs. Tip and toss unnecessary containers. This includes flowerpots, old car tires, rain gutters, and pet bowls. Ensure swimming pools and spas are properly maintained. Consider including mosquitofish in ornamental ponds and fountains.
* Avoid outdoor activity at peak times when mosquitos are most active: early morning (dawn) and evening (predusk).
* Protect yourself by wearing long-sleeved shirts and pants during peak biting times. Also, when outdoors, apply EPA-registered insect repellent that contains one of these active ingredients: DEET, Picaridin, IR3535, Oil of Lemon Eucalyptus (OLE), or Para-menthane-diol (PMD). Follow all label instructions.
Additionally, if you find a dead bird (especially a crow, jay, magpie, raven, sparrow, finch, or hawk), file a report online at westnile.ca.gov or call toll-free 1-877-968-2473 (1-877-WNV-BIRD) to report it. Contact San Joaquin County Mosquito & Vector Control District at sjmosquito.org to report significant mosquito infestations, daytime biting, or neglected (green) swimming pools. The agency also provides mosquitofish for ponds and other man-made water features. These fish feed off mosquito larvae and naturally help control mosquito populations. For current information on California WNV resources and statistics, visit westnile.ca.gov.
