NYC West Nile Virus Cases Surpass 2025 Total

The number of New York City residents diagnosed with West Nile virus this year has already exceeded the total cases reported in 2025. As of the latest data, at least 30 people have contracted the mosquito-borne illness, a significant increase from the 18 cases recorded in the entirety of 2025. Brooklyn has reported the highest number of cases with 11, followed by Queens and Staten Island with seven each. The Bronx has seen three cases, and Manhattan has recorded two.

Of the 30 confirmed cases this year, 24 are classified as the more severe West Nile neuroinvasive disease, which can lead to conditions such as encephalitis, meningitis, or acute flaccid paralysis. The remaining six cases are categorized as West Nile fever, which does not involve the central nervous system.

The city has also observed a record number of positive mosquito pools, with over 1,700 samples testing positive for the virus in 2026, compared to just over 1,300 in the previous year. This surge in both human and mosquito infections is linked to prevailing weather conditions.

Sally Slavinski, director of the Zoonotic and Vector-Borne Disease unit at the city's health department, explained that warmer temperatures accelerate the mosquito life cycle and speed up viral replication within the insects. "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," Slavinski told Gothamist. She added that increased rainfall and humidity create an environment where mosquitoes can thrive, and longer, warmer seasons allow for more opportunities for transmission.

The health department actively monitors mosquito populations and implements pesticide applications during the summer months to control their numbers. West Nile virus is the only mosquito-borne disease known to spread to humans in New York City and has been present for over 25 years.

While most people infected with West Nile virus do not develop symptoms, approximately one in five may experience a mild illness. Slavinski noted that the high rate of neuroinvasive cases suggests that many milder cases may go unreported, as individuals with mild or no symptoms may not seek testing or medical care. Those who are severely ill, often hospitalized, are more likely to be tested and diagnosed, thus skewing the data towards more severe outcomes.