An acute febrile disease of humans produced by spirochetes of many species of Leptospira. The incubation period is 6–15 days. Among the prominent features of the disease are fever, jaundice, muscle pains, headaches, hepatitis, albuminuria, and multiple small hemorrhages in the conjunctiva or skin. Meningeal involvement often occurs. The febrile illness subsides after 3–10 days. Fatal cases show hemorrhagic lesions in the kidney, liver, skin, muscles, and central nervous system.
Wild rodents are the principal reservoirs, although natural infection occurs in swine, cattle, horses, and dogs and may be transmitted to humans through these animals. Humans are infected either through contact with the urine or flesh of diseased animals, or indirectly by way of contaminated water or soil, the organisms entering the body through small breaks in the skin or mucous membrane.