Human Leptospirosis Infections in New York City Linked to Rat Exposure on the Rise: What You Need to Know

NEW YORK – The New York City Health Department is urging providers to be aware of a continued increase in a potentially fatal bacterial infection transmitted by rats that can infect both people and pets.

Cases of human leptospirosis are still limited (six cases have been reported in the city so far this year), but are increasing. Twenty-four cases were reported in New York City in 2023, the highest total yet, officials say.

Diseases in the city are largely related to exposure to environments and materials contaminated with rat urine, including soil, water, and garbage bags or bags containing food waste.

Symptoms range from fever to headache, chills, muscle aches, vomiting, diarrhoea, cough, jaundice and rash. The incubation period is usually 5 to 14 days, with a range of 2 to 30 days. If left untreated, kidney failure, meningitis, liver damage, and respiratory distress can occur. Leptospirosis is treated with antibiotics, such as penicillin and doxycycline.

In the past 22 years, only 98 locally acquired cases have been reported. Clinically, cases are presented with acute renal and hepatic failure and, sometimes, severe pulmonary involvement. Six of these 98 patients died. In total, the average age of cases was 50 years, generally male (94%), and most often reported in the Bronx (37), followed by Manhattan (28), Brooklyn (19), Queens (10), and Staten Island (4). Human-to-human transmission is rare.

Leptospira bacteria can die within minutes in dry heat conditions or sub-zero temperatures, limiting their survival in cold city winters. Excessive rainfall (we just had the fourth wettest March on record) and unseasonal heat, factors associated with climate change, can support the persistence of the bacteria.

Last year, half of the locally acquired cases were reported in the months of June and October, months that were warmer and more humid, with heavy rain and unusually warm days compared to previous years, officials said. Cheers.

Leptospirosis can also be a life-threatening disease in dogs. Transmission from dog to human is very rare. In early 2022, the deaths of four dogs suspected to be related to leptospirosis prompted an investigation and the closure of a Brooklyn dog park.

Diagnostic tests are available and include PCR in blood, urine and serological tests. A blood test would detect the disease more quickly. Cases must be reported to the city health department within 24 hours.

New York lawmakers are proposing regulations to humanely reduce the population of rats and other rodents. They are considering rat birth control and preventing glue seizures as alternatives to poison or a brutal, slow death. A new rule recently came into effect requiring all businesses to use covered waste containers or face a fine.