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West Nile Virus cases increase by 125% in San Joaquin County

Last month there were only four verified human cases of West Nile Virus in San Joaquin County so far this year.

As of Monday afternoon, according to data provided by the San Joaquin County Department of Public Health to the State of California, that number had jumped to 9 – a 125 percent increase of the mosquito-transmitted disease that has already killed five people in Northern California this year in less than four weeks.

All of the deaths have occurred in September.

According to the California Department of Public Health, two California residents – one from Glenn County and one from Yuba County – died from West Nile-related illness back in early September, and that number has grown to include residents of Placer and Yolo Counties since then.

A fifth person from Butte County died of complications from West Nile Virus on Monday, but won’t be included in the official total until it is updated next week.

The San Joaquin Mosquito and Vector Control District has remained active well into the fall this year thanks to ongoing warm temperatures that allow mosquito breeding to continue. Last week the agency conducted aerial spraying in rural South Manteca and in an area west of Ripon – a sign that mosquitoes carrying the West Nile Virus continue to show up in samples taken in the area – and spraying both aerially and with ground-based boom trucks could continue until a decline in adult mosquitoes carrying the disease is finally observed.

Per capita, there have been more cases of West Nile Virus reported in the 209 area code than anywhere else in the State of California – the 17 total human cases between San Joaquin and Stanislaus County, with a population of around 1.25 million people, is second only to the 21 human cases in Los Angeles County this year, which has a population of more than 10 million.

Those experiencing symptoms that include severe headaches, a stiff neck, disorientation, or confusion are encouraged to seek medical attention immediately. While hospitalization wasn’t called for in some of the cases that have been diagnosed in San Joaquin County this year, it can be necessary for patients with neuro-invasive West Nile Virus – a course of treatment that includes intravenous fluids, respiratory support, and prevention of secondary infections. There is not currently a cure for West Nile Virus, nor is there a vaccine.

Of the total number of cases last year, 65 percent of those in San Joaquin County were of the neuro-invasive type, of which California has some of the highest rates in the nation according to the Centers for Disease Control. Last year there were 509 cases of the virus in California – more than 25 percent of the total cases in America – and 376 of which were neuro-invasive. A total of 28 people died from the disease in California last year, compared to 112 across the nation.

While spraying is used to help keep populations down and prevent infections, residents are urged to take necessary precautions when outdoors, especially in the early morning or late evening dusk hours.

Those include:

*Checking your property for standing water and eliminating it as needed. Abandoned swimming pools were a major breeding ground for mosquitos during the economic downturn, but something as small as an old tire or a bucket that has collected rain or sprinkler water can provide the environment necessary for mosquitos to breed.

*Applying mosquito repellant that contains the ingredients DEET or Picaridin when outdoors in accordance with usage instructions.

*Avoiding being outside when mosquitoes are the most active, which is typically at dawn and at dusk, and especially for the first two hours after sunset.

*Wearing long pants, long-sleeved shirts, and other protective clothing when forced to be outdoors – especially during peak activity times.

*Making sure that windows and doors have tight-fitting screens to keep active mosquitoes outside of the home.

The virus is typically carried by birds and transmitted by mosquitos who feed on their carcasses and then bite humans. The State of California has a website to report dead birds for removal and subsequent study that can be found at

To report unusually strong mosquito infestations or daytime biting contact the San Joaquin Mosquito and Vector Control District at 209.982.4675 or visit them on the web at

To contact reporter Jason Campbell email or call 209.249.3544.