Leptospirosis is a zoonotic disease with epidemic potential, especially after a heavy rainfall, caused by a bacterium called Leptospira. Leptospira interrogans is pathogenic to humans and animals, with more than 200 serologic variants or serovars. Humans usually acquire leptospirosis through direct contact with the urine of infected animals or a urine-contaminated environment. Human-to-human transmission occurs only very rarely. Leptospirosis may present with a wide variety of clinical manifestations, from a mild illness that may progress to a serious and sometimes fatal disease. Its symptoms may mimic many diseases, such as influenza, dengue and other viral haemorrhagic diseases; making the correct diagnosis (clinical and laboratory) at the onset of symptoms is important to prevent severe cases and save lives, primarily in outbreak situations.