New York City has recorded more human West Nile virus cases in 2026 to date than it did in all of 2025, with mosquito season underway across the five boroughs, according to Gothamist.
Sally Slavinski, director of the city health department's Zoonotic and Vector-Borne Disease Unit, warned that the cases most visible in official data are often the most severe — suggesting far more infections go unreported and obscure the true rate of infection.
Here's what to know
As of September, the city confirmed 23 human West Nile virus cases in 2026, a rate already higher than the 18 recorded in 2025.
Of those 23 cases, 18 were identified as West Nile neuroinvasive disease, a more serious form that affects the nervous system. Confirmed infections have been found across New York City and are skewed toward the sickest patients.
Many people infected with West Nile never notice any symptoms, while others have only a mild flu-like illness that can include fever and body aches.
That helps explain why severe illness makes up such a large share of the city's confirmed cases, per Slavinski.
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"Young, healthy people are not even realizing they may be infected or might have some mild illness. These are folks that are not necessarily getting tested, and so we don't know about these folks that weren't sick or had mild illness," she explained.
"But the people that are more likely to get tested, right, these are the people who are really sick; they're getting hospitalized, and they're getting worked up. These are the folks with West Nile neuroinvasive disease."
More background
The city is monitoring the virus in mosquitoes and people.
More than 1,600 mosquito pools have tested positive for West Nile virus in 2026, a record, according to Slavinski.
West Nile is spread mainly by the bite of an infected mosquito, not from person to person. The Centers for Disease Control and Prevention notes that most infections do not lead to illness, but serious cases can cause complications including muscle weakness and brain swelling.
People with weakened immune systems, along with those who have conditions such as cancer, diabetes, high blood pressure, or kidney disease, face higher risk.
Slavinski told Gothamist that adults 65 and older are about three times as likely as younger people to develop neurologic illness.
Slavinski observed that the spike may be tied to weather.
Warmer temperatures, more rainfall, higher humidity, and longer mosquito seasons all boost mosquito reproduction and make it easier for the virus to spread.
What can be done?
To reduce exposure risk, the city's health department recommends limiting time outdoors at dusk and dawn, when mosquitoes are most active, especially during periods of heightened mosquito activity.
The health department also recommends EPA-registered repellents containing DEET, picaridin, IR3535, or oil of lemon eucalyptus. Wearing long sleeves, long pants, socks, and shoes can provide added protection.
The city also advises identifying and addressing places around the home where mosquitoes can breed.
That means draining standing water from buckets, flower pots, and other containers each week. Pools, hot tubs, and ponds should likewise be maintained, covered, or drained when not in use.
"With this increased rainfall and humidity, it makes it easier for mosquitoes to thrive, and then these longer, warmer seasons where we're having mosquitoes appear earlier and are active later in the year, there's more opportunity for transmission to occur," Slavinski warned.
Where can I learn more?
New York isn't the only place seeing West Nile activity rise as weather conditions help mosquitoes spread the virus. These stories cover human cases, severe illness, and mosquito-driven outbreaks from Texas to Kentucky.
• In early September 2025, West Nile symptoms had risen to 40% above normal amid wider warnings.
• In Harris County, Texas, doctors warned a wet spring could fuel mosquito-driven infections.
• In Kentucky, officials cautioned residents that serious illness can occur as West Nile infections trended upward.
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