Leptospirosis

Leptospirosis is a blood infection caused by spirochaete bacteria belonging to the genus Leptospira, which are aerobic, right-handed helical organisms measuring 6-20 micrometers in length. The genus comprises more than 10 pathogenic genetic types capable of causing human disease. As a zoonotic infectious disease, leptospirosis affects both humans and a wide range of animal hosts including dogs, rodents, livestock, and other wild and domesticated species. The bacteria possess an unusual cell wall structure with a fluid outer membrane loosely associated with the cell wall and a periplasmic flagellum enabling characteristic corkscrew motility.

Clinical presentation of leptospirosis ranges from completely asymptomatic infection to severe, life-threatening illness, with approximately 90% of cases experiencing mild symptoms while 10% progress to severe disease. The illness typically follows a biphasic course: the initial acute or leptospiremic phase lasts five to seven days and presents with fever, severe headache, myalgia, and chills, followed by a second immune phase during which antibodies develop but additional complications may emerge. Severe manifestations include Weil's disease, the acute fulminant form characterized by jaundice, acute kidney failure, and hemorrhage; meningitis; and severe pulmonary haemorrhage syndrome with diffuse alveolar hemorrhage. The incubation period usually ranges from one to two weeks but may extend up to one month, complicating epidemiological tracing.

Leptospirosis demonstrates a global distribution with endemicity in tropical and subtropical regions where warm, humid conditions favor environmental persistence of the organism. The disease exhibits marked epidemiological heterogeneity between developed and developing countries: in low-resource settings with inadequate sanitation, transmission occurs year-round among pest control workers, farmers, and low-income urban populations, while in high-income countries cases cluster around heavy rainfall events and flooding, affecting sewage workers, pest controllers, and participants in outdoor recreational activities in warm, wet areas. Environmental factors including climate change, extreme weather events, urbanization, and inadequate waste management have intensified transmission dynamics by promoting rodent reservoir populations and facilitating spread of contaminated water. The disease burden is substantially underreported due to limited diagnostic capacity in endemic regions and nonspecific clinical presentation.

Leptospirosis is primarily transmitted through contact with water, soil, or vegetation contaminated with urine from infected animals, particularly rodents which serve as the principal reservoir hosts. Human infection occurs when the bacteria enter the body through mucous membranes of the eyes, nose, or mouth, or through breaks in the skin during exposure to contaminated environments. The organism survives in warm, humid environments and has been detected in ponds, rivers, puddles, sewers, agricultural fields, and moist soil, where it may persist within aquatic biofilms. Both wild and domestic animals including livestock and companion animals can shed leptospira in their urine, creating multiple transmission pathways for human exposure.

Occupational groups at elevated risk include agricultural workers, particularly rice farmers and those with livestock contact; pest control workers; sewage and wastewater workers; and veterinarians handling infected animals. Recreational risk factors encompass freshwater swimming, kayaking, and other water sports in endemic areas, especially following heavy rainfall. In developing countries, low-income populations residing in areas with inadequate sanitation face heightened exposure due to rodent infestation and contaminated water sources. Climate-related disasters disproportionately affect homeless populations and those residing in flood-prone informal settlements, creating outbreak vulnerabilities in marginalized communities.

Effective prevention of leptospirosis requires coordinated One Health interventions spanning human, animal, and environmental health sectors. Public health strategies include strengthening surveillance systems for outbreak detection in flood-prone regions and areas with poor sanitation, improving laboratory capacity for early diagnosis, and implementing rodent control programs to reduce reservoir populations. Animal health interventions encompass vaccination of livestock and domestic animals against leptospira, while occupational health measures include provision of protective equipment for workers at high risk of exposure. Environmental interventions focus on improved waste management and flood mitigation infrastructure to reduce contamination of water sources with animal urine.

Leptospirosis surveillance presents particular challenges due to the disease's nonspecific initial symptoms resembling other febrile illnesses, resulting in substantial underascertainment in many regions. Monitoring should incorporate One Health data streams integrating human case reports, animal reservoir surveillance, and environmental sampling for leptospiral contamination. Seasonal patterns linked to rainfall and flooding events should inform anticipatory surveillance during high-risk periods. Enhanced laboratory capacity for serological testing and molecular detection is essential for accurate case confirmation and outbreak investigation. Surveillance data should be interpreted with awareness that case numbers likely represent only a fraction of true incidence, particularly in resource-limited settings with limited diagnostic infrastructure.

1. 1 WHO Fact Sheet. Detail.
2. 2 WHO Q&A. News.
3. 3 Wikidata. leptospirosis.
4. 4 Wikipedia. Leptospirosis - Wikipedia.

ICD-10

A27

ICD-11

1B95

Total cases

10K

Total deaths

61

Peak month

2014-12

Coverage

4 reporting countries · 2000-01-01 → 2026-05-09