Human infections from rat urine on the rise in New York City

The New York Department of Health and Mental Hygiene has released a health advisory after multiple cases of human leptospirosis -- an infection that is associated to exposure to rat urine -- have been reported so far this year in New York City.

There were 24 cases of leptospirosis in the city in 2023, higher than in any prior year, according to the NYC Department of Health and Mental Hygiene.

However, in the first quarter of this year alone, there have already been six to date.

“For comparison, the average number of locally acquired cases during 2021 to 2023 was 15 per year, and 3 cases per year during 2001 to 2020,” health officials said. “This year, 6 cases have been reported as of April 10, 2024.”

“Among the 98 locally acquired cases reported from 2001 to 2023, the median case age was 50 years (range 20 to 80 years), usually male (94%) and, reported most often from the Bronx (37), followed by Brooklyn (19), Manhattan (28), Queens (10), and Staten Island (4),” said the NYC Department of Health and Mental Hygiene.

Those suffering from severe leptospirosis have acute renal and hepatic failure and, occasionally, severe pulmonary issues, health officials in New York City said. However, symptoms may include fever, headache, chills, muscle aches, vomiting, diarrhea, cough, conjunctival suffusion, jaundice, and rash, the city said.

The incubation period is usually 5 to 14 days but it is possible for it to last between 2 to 30 days. If leptospirosis is not treated, kidney failure, meningitis, liver damage, and respiratory distress can occur.

There were a total of six deaths caused by leptospirosis from 2001 to 2023 in New York City, according to the NYC Department of Health and Mental Hygiene.

“In NYC, locally acquired cases typically have a history of a residential or occupational exposure to rat urine or environments (including soil and water) and materials contaminated with rat urine (e.g., handling trash bags or bins containing food waste), health officials said in their press release regarding the uptick in cases of leptospirosis. “Person-to-person transmission is rare. The NYC Health Department conducts inspections and works with property owners to remediate rat conditions, if indicated.”

According to the NYC Department of Health and Mental Hygiene, leptospira bacteria are fragile and can die within minutes in dry heat or freezing temperatures.

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

In 2023, half of the locally acquired cases were reported in the months of June (5) and October (5), months that were warmer and wetter with excessive rain and unseasonably warm days compared to prior years, according to the NYC Department of Health and Mental Hygiene.

Cases of leptospirosis must be reported to the NYC Health Department within 24 hours and more information about the illness can be found on the New York City Health Department and CDC websites.

“As always, we appreciate your collaboration in improving the health of New Yorkers and helping us direct remediation efforts in New York City,” said Celia Quinn, Deputy Commissioner of the Division of Disease Control in New York City.