California’s second case of West Nile Virus of the year has been confirmed in San Joaquin County.

A 49-year-old man is currently receiving treatment for the virus in a local healthcare facility, according to the county’s health department.

Tulare County public health officials confirmed last week the state’s first infection in humans for 2023. San Joaquin and Tulare counties have also had the largest number of instances of West Nile Virus in mosquito samples, according to the state.

West Nile Virus is transmitted to both animals and humans through mosquito bites. Symptoms include severe headaches, stiff neck, disorientation and confusion.

“Most people who become infected do not get sick, and the risk of serious illness to most people is low,” Maggie Park, SJ County public health officer, said in a statement Thursday. “However, about 1% of individuals can develop a serious neurologic illness, such as encephalitis and meningitis.”

Those who have been bitten by a mosquito and are experiencing symptoms should seek medical attention immediately, public health officials say.

Since 2003, there’s been more than 7,500 human cases and 300 deaths from West Nile Virus reported in California. It is the most common, as well as the most serious, vector-borne disease in the state. About 24 counties report West Nile Virus activity, according to the state’s Department of Public Health.

Mosquito populations have increased across the state this year due to recent heavy rains over the winter months, the state says, making way for greater risk of mosquito-borne diseases.

“Many of us enjoy spending time outdoors, especially during the summer months, and this year it is particularly important to take extra precautions against mosquitoes,” State Public Health Officer Tomás Aragón said in a statement last month. “The best way to prevent diseases that are spread by mosquitoes is to protect yourself, your family, and pets from mosquito bites.”

The virus has no known cure or vaccine to prevent illness, but can be treated with intravenous fluids, respiratory support and prevention of secondary infections.

SJ County health officials are urging the public to take precautionary measures to avoid being bitten by mosquitos, such as draining any standing water where the insects may lay eggs and avoiding outdoor activities during the peak mosquito hours of the early morning and evening, as well as wearing bug spray and protective clothing, such as log sleeves and pants, when mosquitos are most active. It’s also important to properly maintain pools, spas and ornamental ponds and fountains.

Dead birds should also be reported to the state online at or by calling (877) WNV-BIRD, state and local officials say. To report significant mosquito infestations or neglected — particularly green — swimming pools, contact the county’s Mosquito and Vector Control District online at or by phone at (209) 982-4675 or (800) 300-4675.

For more information, go to the state’s mosquito bit tool kit: here.

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