Leptospirosis in New York City — What Residents and Property Owners Need to Know
Leptospirosis is a bacterial infection transmitted through contact with rat urine. NYC DOHMH documented outbreaks in 2023 and 2024. The highest risk is in neighborhoods with the most severe rat pressure.
Medical notice: This page provides general public health information only. It is not medical advice. Anyone who may have been exposed to rat urine or who is experiencing symptoms should contact a physician or emergency provider immediately.
How Leptospirosis Spreads in NYC
Leptospira bacteria are shed continuously in rat urine. A single Norway rat — the dominant species in NYC — deposits urine dozens of times per day across its home range. The bacteria survive for weeks in moist, cool environments, particularly in basement floors, soil near burrow entrances, and drainage infrastructure.
NYC's combination of dense rat populations, aging housing stock with flooding-prone basements, and urban gardening activity in high-pressure neighborhoods creates exposure pathways that are more concentrated than in most US cities.
The most common exposure scenarios the DOHMH identified in the 2023 and 2024 outbreak investigations were:
- Cleaning or working in flooded basements in rat-infested buildings
- Gardening in soil contaminated with rat urine near active burrow zones
- Handling materials stored in infested areas without gloves
- Wading through standing water in alleys or building courtyards with active rodent activity
Symptoms to Watch For
Seek medical attention immediately if you experience fever, severe headache, muscle aches, or red eyes after potential exposure to rat urine or contaminated flood water in NYC.
Leptospirosis presents in two phases. The first phase — lasting 3 to 7 days — typically includes sudden fever, intense headache, muscle pain particularly in the calves and lower back, chills, red eyes (conjunctivitis), and sometimes rash.
A brief improvement period can follow. The second phase, when it occurs, can involve kidney or liver involvement (Weil's disease), meningitis, and respiratory distress. Early antibiotic treatment is highly effective. Delayed treatment of severe cases can be life-threatening.
Highest-Risk NYC Neighborhoods
DOHMH case data from 2022 through 2024 identifies these areas as having the highest documented leptospirosis risk linked to rat exposure.
Hunts Point, South Bronx
Food market complex sustains the largest urban rat population in NYC. Bronx River proximity. Highest case rate per capita per DOHMH data.
East Harlem, Manhattan
Dense NYCHA building concentration, aging infrastructure, and 125th Street displacement pressure. Community garden activity near burrow zones.
Bushwick, Brooklyn
Industrial-to-residential buildings with basement flooding risk during heavy rainfall. 2024 cases included confirmed basement flood exposures.
East New York, Brooklyn
Older residential stock, high rat infestation rates, and basement flooding in aging drainage infrastructure. Top 5 for related ED visits 2021–2024.
Map of High-Risk Areas
How Rodent Exclusion Reduces Your Risk
The most effective intervention for reducing leptospirosis risk in a building is eliminating rat access entirely. When rats cannot enter, urine contamination accumulates at a far lower rate and natural cleaning of affected surfaces stops the cycle.
Professional Inspection
A licensed contractor maps all rat entry points — utility penetrations, foundation voids, party wall access, drain connections — before any sealing begins.
Population Elimination
Treatment reduces existing rats before exclusion seals entry points. Sealing without treatment traps live rats inside, worsening the problem.
Permanent Entry Point Sealing
Stainless steel mesh, hydraulic cement, and hardware cloth at every identified gap. Materials that rats cannot chew through, sized appropriately for each opening.
HEPA Cleanup of Affected Areas
After exclusion, HEPA vacuuming of basement and floor areas removes dried urine particles that can become airborne in confined spaces. Reduces residual contamination risk significantly.
Frequently Asked Questions
Permanent Exclusion Stops the Source of Contamination
Request a professional assessment. A licensed contractor will map every rat entry point and provide a written scope before any work begins.
Sources: NYC DOHMH Communicable Disease Data; NYC DOHMH Rat Information Portal; CDC Leptospirosis guidance. This page is for general public health education only and is not a substitute for professional medical advice.