Leptospirosis, a bacterial infection (aka rat fever), surges during the monsoon because Leptospira bacteria thrive in warm, humid, waterlogged environments, especially when animals contaminate floodwaters with urine. It enters the body through skin cuts, abrasions, or mucous membranes during contact with contaminated water or soil.

Early symptoms fever, headache, muscle pain mirror flu or dengue, often leading to misdiagnosis. If unchecked, it can escalate into severe conditions like Weil’s disease, causing jaundice, kidney or respiratory failure, and meningitis.

High-risk groups include those wading through waterlogged streets, sanitation workers, farmers, sewage handlers, and residents of flood-prone or rodent-infested areas. For instance, Mumbai, with over 143 cases recorded in July, and Kerala’s Ernakulam district, reporting 15 deaths in the first seven months of 2025, highlight this seasonal vulnerability. Delays in diagnosis and treatment often worsen outcomes.

Prevention starts with avoiding contact with stagnant or floodwater and maintaining hygiene: wash limbs after exposure, wear protective gear like waterproof boots and gloves, and avoid playing or wading in contaminated water bodies especially children.

Health authorities also recommend prophylactic doxycycline for high-risk individuals during heavy monsoon exposure. This and other prevention strategies like improving sanitation, rodent control, and early case detection are part of broader public health guidance.