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West Nile Virus Information

West Nile Virus (WNV) is a mosquito-borne virus that can cause encephalitis (inflammation of the brain) or meningitis (inflammation of the lining of the brain and spinal cord). Only an estimated 1-3% of WNV infections, result in serious disease. Most people who are infected will show no symptoms at all, or have mild flu-like symptoms such as headache, fever and body aches. Rarely do symptoms get more severe.

WNV Cycle

WNV is spread by mosquitoes that feed on infected birds that have migrated into an area. The mosquitoes then bite people or horses, who may or may not become infected.

Encephalitis is not spread by person-to-person contact, nor animal to human contact. The cycle of WNV occurs at an unusually high intensity when there is both a large number of infected birds and a high rate of mosquitoes in a relatively small geographic area.

Mosquito Activity

Mosquitoes are the known carriers (vectors) of the viruses from the host birds to humans. Humans and animals are incidental hosts in this bird-mosquito cycle.

If you are currently experiencing mosquito activity in your area, please report this activity to MCESD Complaint Line at 602-506-6616 or file your mosquito activity concern at:
Mosquito Complaint Form

The following are guidelines to minimize the risk of mosquito-borne illnesses:

  • Eliminate standing water, which allows mosquitoes to breed. Check for items outside the home that collect water, such as cans, bottles, jars, buckets, old tires, drums and other containers.

  • Change water in flower vases, bird baths, planters and animal watering pans at least twice a week.

  • Repair leaky pipes and outside faucets, and move air conditioner drain hoses frequently.

  • Avoid bites when going outside at night in areas where mosquitoes are present by using insect repellent.

  • Wear light-weight clothing that covers the arms and legs.

For more information on West Nile Virus:

See our mosquito fogging schedule for Maricopa County
Fogging Schedules

See the CDC website at:

Visit the Maricopa County Public Health website.