NYC Health Department Detects Increase in Mosquitos with West Nile Virus Across New York City

NYC Health Department Detects Increase in Mosquitos with West Nile Virus Across New York City

NYC Health Department Expands Mosquito Surveillance and Control

No Human Cases of West Nile Virus Have Been Reported Yet in New York City This Season

New Yorkers Are Urged to Take Simple Steps to Prevent Mosquito Bites

Mosquito Control Operations Can Reduce West Nile Virus-Positive Mosquito Pools by More Than 85%

August 6, 2026 - The New York City Health Department announced today that West Nile virus has been detected in nearly twice as many mosquito pools as this time last year and is urging New Yorkers to take simple precautions to protect themselves from mosquito bites.

Mosquitoes carrying West Nile virus are present in New York City every year from June through October, with activity typically peaking during August and September. The virus spreads to people through the bite of an infected mosquito. While no human cases have been reported in New York City this season, cases are typically seen between mid-July and early fall.

In response, the Health Department has intensified mosquito surveillance in affected areas by deploying additional traps and expanding mosquito control efforts. Enhanced larval control is also underway to reduce mosquito populations before they become capable of transmitting disease.

The Health Department operates one of the nation's most comprehensive mosquito surveillance programs, monitoring mosquito populations throughout all five boroughs from spring through fall. Each week, trained staff collect mosquitoes from hundreds of locations across the city. The mosquitoes are grouped into samples, or "pools," with up to 50 mosquitoes tested together for the presence of West Nile virus.

Since July, the Health Department has conducted four targeted mosquito control operations in neighborhoods where 315 West Nile virus-positive mosquito pools were detected. These operations typically reduce adult mosquito populations by about 70% and decrease West Nile virus-positive mosquito pools by more than 85%, helping to reduce the risk of human infection. Additional control operations are planned for the coming weeks. Information about completed and upcoming mosquito control operations is available at nyc.gov/mosquito.

"The detection of West Nile virus in mosquitoes demonstrates that New York City's mosquito surveillance system is working exactly as intended," said NYC Health Commissioner Dr. Alister F. Martin. "Our system allows us to identify where the virus is circulating early and take targeted action to reduce mosquito populations before more people are at risk. Earlier this summer, we completed four mosquito control operations over select nonresidential wetlands and marsh areas. Now is the time for every New Yorker, especially older adults and people with weakened immune systems, to take simple precautions to prevent mosquito bites."

As of July 25, 2026, the Health Department had identified 612 West Nile virus-positive mosquito pools citywide (out of 2,040 pools tested) through its routine mosquito surveillance program. At this time last year, 326 positive mosquito pools had been identified out of 2,040 tested. The first positive mosquito pools this year were detected on June 16, compared with July 1 last year. While the Centers for Disease Control and Prevention is reporting higher than usual West Nile virus activity in other parts of the country, primarily in Arizona, it is difficult to compare New York City's findings with other parts of the country given the City's robust mosquito surveillance.

New Yorkers can view the locations of mosquito pools that have tested positive for West Nile virus by visiting the Health Department's Positive Mosquitoes Map.

The City's integrated mosquito management program includes routine larvicide treatment of catch basins and other breeding sites, enhanced surveillance, public education, and targeted mosquito control measures when data indicate an increased risk of disease transmission. Residents should also eliminate standing water (PDF) on their property to help prevent mosquitoes from breeding.

The Health Department uses an integrated mosquito management approach that combines surveillance with targeted mosquito control methods to reduce the risk of mosquito-borne disease while minimizing pesticide use. This includes:

• Aerial larviciding (helicopter applications): An environmentally friendly biological larvicide is applied over nonresidential marshes, wetlands, and other large natural mosquito breeding habitats to control mosquito larvae before they become biting adults. Helicopter applications are not conducted over residential neighborhoods.
• Truck-based adulticiding (spraying): Adult mosquitoes are treated in selected neighborhoods where surveillance indicates an elevated risk of West Nile virus transmission. Spraying takes place during the evening in residential areas and parks to reduce populations of adult mosquitoes.

The Health Department notifies the public at least 24 hours before any pesticide application and targets mosquito control efforts where virus activity is highest while minimizing pesticide use.

What Is West Nile Virus?

West Nile virus is the only mosquito-borne disease known to spread to humans in New York City. It has been detected in city mosquitoes every year since 1999.

Most people infected with West Nile virus never develop symptoms. Approximately one in five may experience a mild illness that can include fever, headache, body aches, fatigue, nausea, vomiting, or rash. In rare cases, West Nile virus can cause severe neurologic illness including encephalitis or meningitis.

Laboratories and healthcare providers are required to report diagnosed cases of West Nile virus to the Health Department.

Protect Yourself From Mosquito Bites

New Yorkers can significantly reduce their risk by taking a few simple precautions:

• Reduce your risk of bites
• • Limit outdoor activities during dawn and dusk, when the mosquitoes that transmit West Nile virus are generally most active.
  • Use an EPA-registered insect repellent containing DEET, picaridin, IR3535, or oil of lemon eucalyptus. Follow the product label. Oil of lemon eucalyptus should not be used on children younger than age 3.
  • Wear long-sleeved shirts, long pants, socks, and shoes when spending time outdoors in areas with mosquito activity.
• Keep mosquitoes out
• • Install and repair window and door screens.
• Prevent mosquito breeding
• • Empty standing water at least once each week from buckets, flowerpots, birdbaths, children's toys, tarps, plant saucers, clogged gutters, and other containers.
  • Maintain swimming pools, hot tubs, and ornamental ponds by keeping them clean, chlorinated, covered, or properly drained when not in use.
  • You can report chronic standing water in private or public locations online or by calling 311. You can report water in the street caused by a street defect or a clogged catch basin online or by calling 311.

For more information about West Nile virus, mosquito prevention, and the Health Department's mosquito control program, visit nyc.gov/health/wnv or call 311.

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