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Mosquito spraying for West Nile virus continues thru Oct.

As long as the temperature is up the mosquitoes will be out.

And for San Joaquin County public health officials and mosquito and vector control staffers, that means at least another month of trying to prevent additional West Nile Virus infections from taking root in the Northern San Joaquin Valley.

With the Labor Day weekend already past, mosquito abatement efforts are near their end, according to San Joaquin Mosquito and Vector Control spokesman Aaron Devencenzi – expected to drop off significantly by the end of October as the first frost finally descends on the Central Valley.

But that means at least another month of conducting ongoing monitoring and eradication as necessary – especially in the worst year for West Nile Virus concentrations since at least 2014.

According to a five-year analysis of mosquito trap results – which can isolate a single mosquito as a carrier of West Nile Virus – the concentration of the virus is up significantly over the five-year average, and is only eclipsed by the 2014 numbers that were slightly higher than what was discovered through the end of August.

When looking at the same results on a regional level, San Joaquin, Stanislaus and Sacramento Counties have eclipsed Los Angeles County as the area of the state with the highest concentration of both affected mosquitoes and live human cases – prompting an all-out effort by abatement districts to corral the adult populations as they’re discovered.

The area’s close proximity to the Southern San Joaquin Valley is of particular concern to people like Devencenzi that are constantly monitoring for the arrival of a different type of mosquito – one that bites during the daylight hours – that can carry other deadly communicable diseases.

Mosquitos that are capable of carrying both the Zika virus and Valley Fever have been found as close as Merced, and preventing their arrival in the Northern San Joaquin Valley is something that the district is hoping that a coordinated spraying effort – through the utilization of aerial spraying and the use of ground trucks with spray booms – will prevent that population from taking root.

This week aerial spraying will be taking place over the Delta islands and parts of Western and Southwestern Stockton – where the West Nile Virus was initially discovered this year – after recent tests showed a concentration of mosquitoes carrying the virus. While a large portion of the spraying will take place over rural areas outside of Stockton’s city limits, Devencenzi said that the Van Buskirk area will also be included because of what was discovered when recent traps set in the area were sent to their lab for analysis.

As of the end of August four people in San Joaquin County have contracted the virus from infected mosquitoes while five people in nearby Stanislaus County – just across the Stanislaus River from Ripon and rural Escalon – have been infected.

Devencenzi said that spraying will continue as long as the tests being conducted on mosquitoes trapped throughout the county warrant it, and as long as the weather continues to create environments in which mosquitoes thrive. While that can drop off as early as the beginning of October, the time frame is fluid and based on the overall temperature across the region.

To contact reporter Jason Campbell email or call 209.249.3544.