New York Suffers Record Rise in Potentially Deadly Disease Caused by Rat Urine

Members of "The Ryder's Alley Trencher-fed Society (R.A.T.S.)" meet with their dogs to vermin control a neighborhood in lower Manhattan in New York on May 14, 2021. Angela Weiss/AFP via Getty Images

New York City has seen a record jump in the number of human leptospirosis, a disease caused by rat urine that can cause kidney damage, liver failure, and even death.

The city’s Department of Health and Mental Hygiene issued an advisory on April 12, warning that the number of human leptospirosis cases continues to trend upward.

The agency said that 24 cases were reported in New York City in 2023, the highest number in a single year on record.

In fact, 6 cases have been reported so far in 2024, twice as high as the average annual number of cases between 2001 and 2020.

While human leptospirosis infections can be caused by contaminated soil and water during natural disasters like floods and hurricanes, in New York they’re mostly caused by rat urine.

Leptospirosis is a zoonotic disease caused by several species of bacteria. In New York, it’s mostly associated with the Norway rat.

“Infected animals excrete the bacteria in their urine, and bacteria can persist in warm, moist environments for weeks,” the advisory states.

“Transmission occurs through direct contact with infectious urine or urine contaminated water, soil, or food, entering the body through open wounds or mucous membranes.”

In New York, the average number of locally acquired cases of the disease was 15 per year during 2021–23. That number was just 3 per year on average between 2001 and 2020.

There have been six deaths associated with the disease in New York between 2001 and 2023, with cases of acute renal and hepatic failure, and occasionally severe pulmonary distress.

While it’s unclear what accounts for the rise in infections, the city’s health department suggested excessive rain and unseasonably warm temperatures may have something to do with it.

Rat Czar

The alarming advisory comes exactly a year after New York City Mayor Eric Adams appointed Kathleen Corradi as the city’s first-ever citywide director of rodent mitigation, which his office dubbed the “rat czar.”

“New York City has done a lot recently when it comes to fighting public enemy number one: rats,” Mr. Adams said in a statement on April 12, 2023. “But it was clear we needed someone solely focused on leading our rat reduction efforts across all five boroughs.”

The appointment of Ms. Corradi as “rat czar” came as Mr. Adams’s office announced a $3.5 million investment in an accelerated rat reduction plan.

Earlier in 2022, Mr. Adams signed four pieces of legislation to fight rats.

“Today, we’re making clear that rats don’t run our city. New Yorkers do,” Mr. Adams said at a press conference on Nov. 18, 2022.

“The four bills I sign today will help create a cleaner city for New Yorkers,” he said. “The legislation will create rat mitigation zones, codify garbage set out times, and reduce rats in construction areas and other buildings with large rodent infestations.”

While it’s unclear how many rats there are in New York City, research in mid-2023 from MMPC Pest Control suggests the city’s rat population has grown to around 3 million.

To come up with this estimate, the company said it used the same methodology used in 2014 by statistician Jonathan Auerbach, who said at the time that the city’s rat population was around 2 million.

New York City is home to one of the biggest populations of Norway rats, which are known to infest buildings and spread disease.

“Unfortunately for New Yorkers, they’re a difficult problem to solve. Rats are intelligent and resilient, enabling them to adapt to various environments. They can even learn to avoid traps and baits,” the pest control firm wrote in its analysis.

“And in a bustling place like New York City, where there’s an abundance of food (think overflowing bins, piles of trash bags on curbs, and outdoor dining establishments) as well as hiding places (subway systems, sewers, and construction zones), it’s no wonder they’re thriving,” it added.

‘This Is a Crisis’

Besides the legislation and the appointment of a rat czar to deal with the city’s rat population, there’s also an effort underway to sterilize the rodents to reduce their numbers.

New York City Council Member Shaun Abreu, a Democrat, recently introduced a bill that would sterilize them by feeding them birth control pellets rather than trying to kill them with poison.

“What’s very important about the rat problem is that we can’t kill our way out of this. This is a crisis. We cannot poison our way out because the growth of rats is so exponential,” Mr. Abreu told Fox 5 NY on April 11.

Mr. Adams said last year that the city’s rat infestation problem is costing New Yorkes and local businesses millions of dollars “to deal with this crisis.”