Rise in Leptospirosis Cases in New York City


The New York City Department of Health and Mental Hygiene reports a record amount of Leptospirosis cases, the zoonotic disease, from rat urine.

rat urine Leptospirosis

Photo of a rat.

Image Credits: Unsplash

The number of reported human leptospirosis cases in New York City (NYC) has significantly risen, marking a new record in 2023 with 24 cases. As of April 10, 2024, 6 additional cases have been reported. Medical providers are urged to consider leptospirosis in patients presenting with symptoms compatible with the disease, particularly when signs of acute renal and hepatic failure are evident. 1

Diagnostic options include PCR testing on blood, urine, and cerebrospinal fluid (CSF) and serological tests, available through most commercial laboratories. It collects samples before initiating antibiotic treatment and submits multiple specimen types for testing.

Main Takeaways

  1. The number of leptospirosis cases in New York City has risen to a record level in 2023, with 24 cases reported and an additional 6 cases noted in early 2024.
  2. Health providers are encouraged to consider leptospirosis in symptomatic patients, especially those showing signs of potential acute renal and hepatic failure.
  3. The rise in cases is associated with environmental exposure to rat urine and conditions favored by climate changes such as increased rainfall and higher temperatures

According to the Centers for Disease Control and Prevention (CDC), “Leptospirosis is a bacterial disease that affects humans and animals. It is caused by bacteria of the genus Leptospira. In humans, it can cause a wide range of symptoms, some of which may be mistaken for other diseases. Some infected persons, however, may have no symptoms at all.”2

In NYC, the primary serogroup identified is Icterohaemorrhagiae, associated with exposure to rat urine or environments contaminated by this urine. From 2001 to 2023, the average annual case count was significantly lower, indicating a notable recent surge. Affected individuals, typically adult males, have been most frequently reported from the Bronx.

Treatment for leptospirosis should commence promptly upon suspicion of the disease, with antibiotics such as doxycycline or penicillin. Providers should also report confirmed cases to the NYC Health Department within 24 hours, utilizing the NYCMED system for expedited communication.

“Without treatment, Leptospirosis can lead to kidney damage, meningitis (inflammation of the membrane around the brain and spinal cord), liver failure, respiratory distress, and even death,” according to the CDC. 2

Environmental factors, including excessive rainfall and warm temperatures likely linked to climate change, may support the persistence of leptospires in the environment. The NYC Health Department continues to monitor and respond to these conditions and assists in remediation efforts to control rat populations, reducing the risk of leptospirosis.

This health advisory reminds healthcare providers to maintain a high index of suspicion for leptospirosis in symptomatic patients, especially those with potential exposure to rat-infested environments. Early recognition, diagnostic testing, and appropriate treatment are crucial in managing and controlling the spread of this potentially fatal disease. For further guidance and support providers are encouraged to contact the NYC Health Department.


  1. 2024 Health Advisory #10: Continued Increase in Leptospirosis Cases in New York City. Published April 12, 2024. Accessed April 19, 2024. chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://www.nyc.gov/assets/doh/downloads/pdf/han/advisory/2024/han-advisory-10.pdf
  2. Leptospirosis. CDC. Published August 30, 2023. Accessed April 19, 2024. https://www.cdc.gov/leptospirosis/index.html
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