Maricopa County Reports Sharp Increase in West Nile Virus Cases and First Deaths of 2026
Key Insights
Maricopa County has reported 25 locally acquired human West Nile virus (search) cases and two deaths through June 18, 2026, a significant increase from 10 cases and zero deaths during the same period in 2025.
The first death of 2026 was an older adult with underlying health conditions; Pima County also confirmed its first West Nile virus (search) case of the year.
About 1 in 5 infected individuals develop flu-like symptoms, while roughly 1 in 150 may experience severe complications such as encephalitis (search) or meningitis (search).
Maricopa County is experiencing a notable surge in human West Nile virus (search) (WNV) cases in 2026, with health officials reporting 25 locally acquired cases and two deaths through June 18, according to the Maricopa County Department of Public Health (search) (MCDPH). This marks a substantial increase from the same period in 2025, when only 10 cases and no deaths had been recorded.
The first fatality of the year was an older adult with underlying health conditions, the county's public health department confirmed in a June 16 news release. The department did not disclose when the individual died, the duration of illness, or the likely timing of the mosquito bite that transmitted the virus.
Regional Spread and Case Counts
The uptick is not confined to Maricopa County alone. The Pima County Health Department (search) confirmed its first West Nile virus (search) case of 2026 on Tuesday, June 16, though no further details about the infected individual, including their condition, were provided.
Earlier in the season, county officials noted that 17 West Nile cases had been reported in Maricopa County as of mid-June, compared to just four cases at the same point in 2025 — underscoring the accelerated pace of transmission this year.
Clinical Presentation and Risk Factors
West Nile virus (search) is primarily transmitted through the bite of an infected mosquito. While most infected individuals remain asymptomatic, approximately 1 in 5 develop a flu-like illness characterized by fever, headache, and body aches. In rarer instances — about 1 in 150 cases — the virus can cause severe neuroinvasive complications, including encephalitis (search) or meningitis (search), which may result in paralysis, long-term disability, or death.
Older adults, people with underlying health conditions, and those with weakened immune systems are at elevated risk for severe illness.
Public Health Response and Prevention Guidance
Melissa Kretschmer, epidemiology supervisor for the Vector-Borne and Zoonotic Diseases program at MCDPH, emphasized the importance of community-level prevention. "As mosquito activity increases across Maricopa County, we encourage residents to take prevention seriously by using insect repellent, eliminating standing water around their homes, and protecting themselves from mosquito bites whenever they spend time outdoors," Kretschmer said.
Kretschmer also highlighted the often-overlooked breeding risks in residential settings: "Even an overturned bottle cap can hold enough water for mosquitoes to breed. It's important that we remove these breeding sources that can form after rain or watering plants."
Public health officials are urging all residents and visitors to remember the "4Rs" framework — Repel, Remove, Repair, and Remind — as a practical guide to preventing mosquito-borne diseases. Maricopa County conducts year-round mosquito abatement efforts, but officials stress that community cooperation in eliminating standing water, particularly after rainstorms, remains critical to curbing transmission.