Leptospirosis is an infectious disease caused by bacteria in the Leptospira bacteria. These bacteria can cause disease both humans and animals, such as dogs, cattle, pigs, horses, rodents, and wild animals. People become infected by drinking or contacting water (such as by swimming, rafting or kayaking) or soil that has been contaminated with these bacteria, or by exposure to the urine or body fluids of infected animals. Symptoms of leptospirosis can develop anywhere from 2 days to 4 weeks after being exposed to the bacteria. Common symptoms of leptospirosis in people include: fever, headache, muscle aches, vomiting, diarrhea and abdominal pain. Leptospirosis can lead to potentially fatal infections of the kidney, liver, brain, lung or heart. Antibiotics are used to treat leptospirosis. Treatment is most effective when started as soon as possible.