Weil's disease, also known as leptospirosis, is a bacterial infection that affects both humans and animals. The disease is caused by the Leptospira bacteria that are commonly found in soil, water, and animal urine. The symptoms of Weil's disease range from mild to severe and include fever, chills, headache, muscle aches, nausea, vomiting, and jaundice. If left untreated, the disease can lead to organ failure and even death. Other synonyms for Weil's disease include mud fever, swamp fever, and rice field fever. These terms are used to describe the disease's association with water and soil, where the bacteria thrive. Prompt treatment with antibiotics can significantly reduce the severity of Weil's disease and increase the likelihood of recovery.