As of September 1, 2026, the CDC has logged 407 human West Nile virus cases, 285 of them neuroinvasive, and 23 deaths in its ArboNET surveillance system, spread across 40 states.
Arizona is driving much of the count, followed by California and Texas. Most of Arizona's cases sit in Maricopa County, in metro Phoenix, where much of this season's death toll has been recorded.
West Nile is the leading cause of mosquito-borne disease in the contiguous US. Symptoms usually start 2 to 6 days after an infected mosquito bite.
The mild form and the rare severe form
The reassuring part first. The CDC says most people infected with West Nile virus do not develop any symptoms at all, and only about 20 percent develop flu-like illness, a form clinicians call West Nile fever. About 1 in 150 infected people go on to severe disease affecting the central nervous system.
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Those two very different pictures produce the seven warning signs worth knowing.
Mild West Nile fever, in roughly 1 in 5 people who are infected:
- Fever with headache
- Body aches and joint pain
- Vomiting or diarrhea
- Rash
Severe neuroinvasive disease, in about 1 in 150 people who are infected:
- High fever with neck stiffness
- Disorientation, stupor or coma
- Muscle weakness, tremors or paralysis
There is no specific antiviral drug for West Nile virus. Anyone with the neurological signs, particularly a stiff neck, sudden confusion or new limb weakness, should be evaluated urgently. Severe cases can cause meningitis or encephalitis and can leave lasting neurological damage.
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Who is at higher risk
The CDC states that people 65 and older are three times as likely as younger adults to develop neurologic illness once infected. Adults with cancer, diabetes, high blood pressure or kidney disease, and anyone on immune-suppressing medication, also face a higher risk of severe illness.
What is happening in New York
New York City confirmed its first human case of 2026 on August 19, in a Manhattan resident who had been outdoors in the city and at several locations outside the five boroughs. By that point more than 1,000 mosquito pools had tested positive for West Nile citywide, with positive pools detected in all five boroughs since June 16.
"West Nile virus is spread by mosquito bites and cannot spread from person to person. The good news is it's preventable," NYC Health Commissioner Dr. Alister F. Martin said in the department's announcement.
Practical steps that actually cut your risk
The CDC's guidance is simple. Use an EPA-registered insect repellent, avoid being outside between dusk and dawn when the mosquitoes that spread West Nile are most active, wear long, loose-fitting shirts and pants, and use screens on windows and doors.
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Around the home, empty standing water weekly from containers, gutters, planters and pool covers, where mosquito larvae develop. Peak US transmission typically runs from late August through the fall, so the 2026 season is not over.
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This article is made and published by Mie Hermansen, who may have used AI in the preparation.