Leptospira is a corkscrew-shaped bacteria that causes an infection called Leptospirosis. The Leptospira bacteria infect many types of animals (many wild animals, rodents, dogs, cats, pigs, horses, cattle, for example) that subsequently contaminate water, lakes, rivers, soil, and crops when they urinate because the bacteria are present in urine. The bacteria then infect humans when they invade through breaks in the skin or mucous membranes or when people ingest them. The bacteria multiply in the liver, kidneys, and central nervous system. The signs and symptoms can range from none to mild such as headaches, muscle pains, and fevers; to severe with bleeding from the lungs or meningitis. Person-to-person transfer of this disease is rare.