[Leptospirosis (Weil's Disease)].

Leptospirosis is a zoonotic infectious disease caused by pathogenic Leptospira species and is characterized by a broad spectrum of clinical manifestations. The disease ranges from a mild, self-limiting illness known as Akiyami to severe Weil's disease, which presents with high fever; jaundice; hemorrhagic tendencies involving the skin, nasal cavity, and lungs; and acute renal failure. Leptospirosis is endemic to many regions of Southeast Asia. In Japan, it occurs most frequently in Okinawa Prefecture. Human infections are primarily acquired through direct or indirect contact with water or soil contaminated with the urine of infected animals. Diagnosis is established using bacterial culture, polymerase chain reaction, and serological testing, which allow accurate detection across different stages of the disease. Treatment typically involves doxycycline for mild-to-moderate cases, whereas penicillin is recommended for severe diseases. Despite advances in its diagnosis and therapy, leptospirosis remains a major public health concern in endemic regions. Therefore, preventive strategies are essential, particularly during the rainy season and following floods or landslides when environmental contamination is more likely to occur. Avoiding unnecessary exposure to potentially contaminated water plays a critical role in reducing the risk of infection.