West Nile Virus Hits City Harder Than Last Year

West Nile virus has made concerning inroads across the five boroughs this year, with 23 total cases identified by health officials as of mid-September, compared to 15 diagnosed throughout all of last year.

Manhattan has not been spared this year. Although the first case of West Nile virus reported by the Health Department was in Manhattan, there has only been one other case in the borough so far this year. Queens, Staten Island, and the Bronx have each seen three cases. Brooklyn, meanwhile, makes up the rest of the total with seven cases.

As first reported by Gothamist, these grim figures aren’t necessarily a departure from historical averages; there were 46 cases diagnosed citywide in 2022, 32 in 2023, and 36 in 2024.

Yet the mosquito-borne disease, health officials stress, poses a serious threat to all New Yorkers—and is being detected in what is known as “mosquito pools” at record rates, with 1,600 receiving positive tests.

Of the 23 cases contracted this year, a total of 18 have given people what is known as West Nile neuroinvasive disease, a progression of the illness that affects the central nervous system and can cause life-threatening meningitis and spinal cord damage. The remaining five people have contracted the less severe, and far more common, iteration of the disease known as West Nile fever.

This inflated percentage of patients who have been diagnosed with the neuroinvasive stage of the disease—which typically affects less than 1 percent of people who contract West Nile virus overall—is tied to the fact that most people who contract West Nile virus don’t report it, given that they have far milder symptoms that resemble a mild flu.

In fact, most people who contract the disease have no symptoms at all. The NYC Health Department estimates that only one in 150 people who are infected with West Nile develop severe neuroinvasive disease.

People who are aged 65 or older are three times more likely to develop West Nile neuroinvasive disease than younger patients, as well as people living with chronic conditions or weakened immune systems.

The record number of infected breeding pools detected citywide are tied to changes in weather trends, health officials say, namely an increase in warm temperatures and rainfall. In fact, warmer temperatures accelerate the mosquito reproductive cycle, leading to population surges and the increased spread of West Nile.

There are steps that local residents can take to stem the tide of West Nile and mosquito breeding pools, which largely amount to removing standing water from anything that it can pool in outside of one’s home, such as flower pots or similar containers.

Pools and hot tubs should also be covered and drained when not in use, officials say. Of course, there are also ways to protect oneself, such as by using insect repellant or wearing clothes with long sleeves.

The first West Nile virus outbreak to be recorded in the United States occurred in New York City back in 1999, when a number of older New Yorkers in Queens started showing up at the hospital with brain swelling. It was originally mistaken for St. Louis encephalitis, a similar virus.