(Bloomberg) -- New York City is seeing a rise in cases of human leptospirosis, a disease caused by rat urine, which if left untreated can cause kidney failure and liver damage.

The city’s Department of Health and Mental Hygiene issued an advisory on Friday after 24 people were diagnosed with the disease in 2023, the highest number in a single year, and six cases were reported so far this year.

The data comes a year after Mayor Eric Adams appointed a “czar” to curb the rat population in the city, which has increased 50% to 3 million since 2010, according to one study. Adams, a vocal rodent antagonist, said he hired the czar for $155,000 to commit to the “wholesale slaughter” of the vermin.

Leptospirosis is caused by several species of a bacteria transmitted through direct contact with infectious urine or urine-contaminated water, soil or food. It enters the body through open wounds or mucous membranes, most commonly causing symptoms from fever to headache and chills. Person-to-person transmission is rare, the city said.

“The cold winters of NYC likely limit the extent to which leptospires can survive in the environment,” the advisory states. “However excessive rain and unseasonably warm temperatures, factors associated with climate change, may support the persistence of leptospires in more temperate areas like NYC.”

Read More: How Climate Change Is Intensifying Dangerous Diseases: QuickTake

--With assistance from John Lauerman.

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