There haven't been any human cases of West Nile virus in Pinal County, and environmental health specialists are fogging for mosquitoes to try to keep it that way.
Garry Bouquot, an environmental health specialist, recently pulled a night shift in Casa Grande to fog an area where a mosquito trap revealed that one of the insects had the virus.
"We fog in areas that have shown positive tests for mosquitoes carrying the virus," he said.
After the fogging, fellow environmental specialist Tami Schuler collects mosquito traps to determine where the virus might be present.
"It's a never-ending process," she said. "We will take the mosquitoes we catch in these traps and test them to see if they carry the West Nile virus."
The county now has its own minilab for testing, with funding from the Arizona Department of Health Services.
"We can be much more proactive now that we have the equipment here, in-house," Schuler said.
The risk of West Nile spreading increases as the monsoon rains help breed more mosquitoes that can transmit the virus to people.
Mosquitoes are most active at dusk and dawn. Bug repellents that include DEET, picardin, oil of lemon, eucalyptus and other ingredients have been shown to be effective.
County officials also recommend that people keep their lawns trimmed and reduce standing water on their property. Tires and empty pots filled with water can be breeding grounds for the pests.