The first West Nile Virus (WNV) positive mosquitoes of the season were found this week during routine surveillance, the Pinal County Public Health Services District said.

Surveillance data is used to help determine the risk of mosquito-borne disease to county residents and visitors, and guides the health department in its disease prevention efforts.

The county did not say where the mosquitoes testing positive were found.

West Nile Virus, a disease spread through the bite of certain mosquitoes, is now common in Arizona. Pinal County’s surveillance program specifically looks for mosquitoes that potentially spread disease to people in the community.

According to the Centers for Disease Control and Prevention, about 1 in 5 people infected with WNV develop a fever with other symptoms – headache, body aches, joint pains, vomiting, diarrhea or rash. Most people infected by the virus recover completely, but fatigue and weakness can last for weeks or months.

About 1 in 150 people who are infected develop severe illness affecting the central nervous system, such as encephalitis or meningitis. Symptoms of severe illness include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. People over 60 are at greater risk for more serious symptoms.

Not everyone who gets mosquito-borne diseases has symptoms, but some may experience lasting or permanent effects, and in the worst cases, the diseases can be fatal. The health department said everyone can help prevent mosquito-borne disease.

“With our monsoon season finally producing some significant rain, it is important that we are all vigilant to prevent mosquito breeding on our property,” said Chris Reimus, manager of Pinal County’s Vector Control program, in a news release.

To help prevent mosquitoes and their bites, health officials recommend that residents:

• Keep swimming pools operational if possible. If it must be out of use, make sure to remove standing water, keep it chlorinated or run the filter daily.
• Eliminate standing water where mosquitoes can lay their eggs. Get rid of outdoor containers that collect water, such as cans, bottles, jars, buckets, old tires and drums.
• Change water in flower vases, birdbaths, planters, troughs and animal watering pans at least twice a week. Be sure to scrub them out when changing water.
• Repair leaky pipes and outside faucets and move air conditioner drain hoses frequently to prevent standing water.
• Be sure to wear protective clothing and use an EPA-registered and CDC-approved insect repellent when outdoors.
• Keep mosquitoes outside with well-fitting screens on both windows and doors.

Pinal County investigates complaints related to disease-causing mosquitoes, such as permanent standing water, green pools, or other reports of mosquito activity. For information on mosquito prevention and control, or to file a complaint, visit the Pinal County Environmental Health Services Pinal.gov/EHS, or call 866-287-0209.