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Health officials in Maricopa County in south-central Arizona are reporting a significant increase in West Nile virus (WNV) cases so far in 2021. Maricopa County is the home to the city of Phoenix.

Maricopa County/ David Benbennick

To date, the Maricopa County Department of Public Health has reported 36 human WNV cases, including one fatality. This compares to three human cases and one death in 2020.

Health officials say the death was in a older adult who also had other health conditions.

West Nile virus is typically spread through the bite of an infected mosquito. Although it can cause severe disease, only about 1 in 5 of those infected will develop any symptoms at all. Those who do develop symptoms usually experience a flu-like illness including fever, headache, body aches and muscle weakness. Rarely, about 1 in 150 people infected can develop encephalitis or meningitis (inflammation of the brain or of the spinal cord). This more severe form of the disease can present with headache, neck stiffness, vision loss, paralysis and other neurologic symptoms. These severe cases can lead to very prolonged illness, permanent paralysis or death. Those who are over 60 years old, have underlying medical conditions or have depressed immune systems are at higher risk for the more severe form of West Nile virus.

Maricopa County Environmental Services Department (MCESD) has seen a nearly 400% increase in positive West Nile virus mosquito samples this year compared to all of last year.

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Maricopa County Public Health offers the following recommendations for avoiding mosquitoes and the diseases they may carry:

  • Avoid mosquito bites day and night
  • Use insect repellent containing DEET, Picaridin, or other EPA-registered repellants according to the product label on exposed skin and clothing
  • Drain and remove containers that hold water from around your home where mosquitoes can breed, such as plastic covers, buckets, old tires, plant trays, pet bowls, toys, and boats
  • Scrape the sides of the dish or inside potted plants where mosquitoes lay their eggs
  • Make sure doors and windows have tight-fitting screens, no holes, and remain closed
  • If it’s not too hot, wear lightweight clothing that covers your arms and legs
  • Ensure that swimming pools and decorative water features are properly maintained

According to the Centers for Disease Control and Prevention (CDC), more than 200 WNV cases have been reported in 29 states, including 10 deaths.