San Joaquin County confirms first human case of West Nile virus this year

Hannah Workman, The Stockton Record
Updated ·3 min read

This year's first human case of West Nile virus in San Joaquin County was confirmed Thursday, San Joaquin County Public Health Services announced.

The patient, a 49-year-old man, is currently receiving treatment at a local healthcare facility.

The West Nile virus is transmitted to humans and animals by the bite of an infected mosquito.

"Most people who become infected do not get sick, and the risk of serious illness to most people is low. However, about one percent of individuals can develop a serious neurologic illness, such as encephalitis or meningitis," said Dr. Maggie Park, San Joaquin County Public Health Officer.

It is the second confirmed human case of the infection in California in 2023. The first was confirmed in Tulare County last week.

Mosquito samples have tested positive for West Nile and St. Louis Encephalitis viruses in multiple locations within Tulare County. There were 89 new West Nile-positive mosquito samples reported in the county last week, according to California Department of Public Health.

This year in California, 533 mosquito samples from 19 counties have tested positive for the virus, according to the state's public health department. More than 7,500 human cases and over 300 deaths have been reported in California since 2003.

The two viruses are similar and are transmitted by the same types of mosquitoes, according to the Centers for Disease Control and Prevention.

Most infected with West Nile will have no symptoms; however, about one in five people will develop a fever with other symptoms from two to 14 days after infection. Severe cases of West Nile virus can affect the central nervous system and result in death or long-term disability.

Most people infected with St. Louis Encephalitis virus will have few to no symptoms. The most common symptoms are mild, flu-like symptoms, including fever and headache, from five to 15 days after infection.

Like the West Nile virus, severe cases of St. Louis Encephalitis can affect the central nervous system, resulting in meningitis, encephalitis, death, or long-term disability.

The best way to prevent West Nile virus infection is to avoid being bitten by mosquitos, public health officials said. To avoid being bitten, residents should take the following precautions:

  • 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 and evening.

  • 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, or Para-menthane-doil. Follow all label instructions.

If bitten, residents should look out for symptoms of severe infection such as severe headaches, stiff neck, disorientation or confusion, and seek medical attention if those symptoms are present.

Those who find a dead bird should avoid bare-handed contact and file a report online at westnile.ca.gov or call 1-877-968-2473. To report significant mosquito infestations, daytime biting, or neglected swimming pools, contact San Joaquin County Mosquito and Vector Control District at sjmosquito.org or (209) 982-4675.

Record reporter Hannah Workman covers news in Stockton and San Joaquin County. She can be reached at hworkman@recordnet.com or on Twitter @byhannahworkman. Support local news, subscribe to The Stockton Record at https://www.recordnet.com/subscribenow.

This article originally appeared on The Record: San Joaquin County confirms human case of West Nile virus