Humans, horses and birds can get infected with the West Nile virus through a single mosquito bite.

FLORENCE — During seasonal mosquito surveillance this week the Pinal County Public Health Services District detected the first West Nile virus-positive mosquitoes in the county.

Mosquito surveillance is done throughout Pinal County in order to determine the relative risk of mosquito-borne disease to communities.

Vector control specialists hang traps to catch mosquitoes, identify the mosquitoes to determine if they are the type that carry disease and check to see if the virus is present in the mosquitoes caught.

This data is used to help determine the risk of mosquito-borne disease to Pinal County residents and visitors, and it guides the county’s disease-prevention efforts.

“This is a good time to remind people that the best ways to prevent mosquito-borne illness are for residents to stop mosquito breeding on their property by checking for and emptying any standing water,” Chris Reimus, who manages Pinal County’s vector control program, said. “Even a short time outdoors can be long enough to get mosquito bites, so take care to wear protective clothing and use an effective insect repellent.”

The health district is not releasing what part of the county the infected mosquitoes were found in, according to Joe Pyritz, a spokesman for Pinal County. Rather, he said, people need to understand that West Nile-infected mosquitoes could be found anywhere in the county.

Pyritz added that so far this year only a few infected mosquitoes have been found, but they have been found annually since 2010.

Pryitz said there are a “handful” of human cases of West Nile each year, but none has been diagnosed in 2019.

The health district urges people to prevent their exposure to mosquitoes altogether by using the following guidelines:

  • Eliminate standing water where mosquitoes can lay their eggs. Check for items outside the home that collect water, such as cans, bottles, jars, buckets, old tires, drums and other containers and dispose of them.
  • 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.
  • Keep swimming pools and backyard ponds operational. If it is not used, make sure to remove the standing water, keep it chlorinated or run the filter daily.
  • Keep mosquitoes outside the home by having well-fitting screens on both windows and doors.

When using an insect repellent, make sure it is proven effective. EPA-registered and CDC-recommended insect repellents include: DEET, Picaridin, IR3535, oil-of lemon-eucalyptus, para-menthane-diol and 2-undecanone.

When using sunscreen, always apply the sunscreen before applying the insect repellent.

West Nile virus is spread through the bite of certain mosquitoes and is now common in Arizona. Other mosquito-borne diseases, including Zika virus, are emerging into North America but have not yet been spread locally in Arizona.

Pinal County’s mosquito-surveillance program specifically looks for mosquitoes associated with human disease.

Not everyone who gets mosquito-borne diseases has symptoms, but for those who do some may experience lasting or permanent effects, and in the worst cases the diseases can be fatal.

Pinal County also investigates complaints related to disease-causing mosquitoes, such as permanent standing water, green pools or other reports of mosquito activity.

For more information on mosquito prevention and control, or to file a complaint, visit the Pinal County Environmental Health Services webpage at or call 866-287-0209.