Nearly two dozen people have been diagnosed with West Nile Virus in New York City so far this year, according to the city’s health department data.
The 23 cases of the virus are scattered throughout the city, with three in the Bronx, seven in Brooklyn, two in Manhattan, three in Queens and three on Staten Island.
That’s more than the 18 confirmed cases in the city in all of 2025 — but that year was lower than other recent years. There were 36 confirmed cases in 2024, 32 in 2023 and 46 in 2022.
The disease, which is primarily spread through bites from infected mosquitoes and doesn’t spread person-to-person, can range from mild to severe. According to the Centers for Disease Control and Prevention, most people who get the virus don’t develop any symptoms at all. Some people can develop mild flu-like symptoms, such as fever and body aches. Some can develop more severe illness that can affect the central nervous symptoms and cause muscle weakness and brain swelling, according to the city's health department.
In New York City, of the 23 people with confirmed cases, 18 were categorized as having West Nile neuroinvasive disease, the more severe outcome of the disease. The five others were categorized as having West Nile fever, with no evidence of central nervous system involvement.
According to city official Sally Slavinski, director of the city health department's Zoonotic and Vector-Borne Disease Unit, the higher proportion of confirmed neuroinvasive cases reflects that most infected people don’t get sick enough to seek medical care.
“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 said. “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.”
According to the city’s health department, one in 150 people develop severe disease, meaning for each confirmed severe case the city logs, there are up to 149 others with no symptoms or very mild symptoms.
City health officials monitor not only cases of the disease, but also its presence in mosquito pools across the five boroughs. So far this year, more than 1,600 mosquito pools have tested positive for the disease — a record number, according to Slavinski. She said that climate change is likely a factor, with mosquitoes thriving in warmer and longer summers, making transmission more likely.
“We know that warmer temperatures can accelerate the mosquito life cycle and speed up viral replication in the mosquito, so that's gonna shorten the time that it takes for there to be an infected mosquito and then transmit that virus,” she said. “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 said New Yorkers should be aware of their risk for becoming severely ill if infected with West Nile virus. For example, people 65 or older are three times more likely to develop neurologic illness than younger people. People with chronic conditions such as cancer, diabetes, high blood pressure or kidney disease, and those with weakened immune systems are also at higher risk.
To reduce their risk of bites, New Yorkers should limit their time outdoors during dusk or dawn when mosquitoes are most active, use EPA-registered insect repellent containing DEET, picaridin, IR3535, or oil of lemon eucalyptus, and wear long-sleeved shirts, long pants, socks, and shoes, according to health officials.
To prevent mosquito breeding, New Yorkers should empty standing water from buckets, flower pots, and other containers at least once a week, and keep swimming pools, hot tubs, and ponds clean, covered, or drained when not in use, according to the health department.
