SummaryLeplospirosis is an million caused by a spirochete called Leptospira, frequently found in water and mud. A cosmopolitan zoonosis. it particularty affects rats. pigs. Cattle and dogs and is directly transmissible of man. although it is most frequently through indirect transmission. following contact with water contaminated by the urine infected animals, dial man coniracts the disease.The large majority of human clinieal forms is anieterie with or without symptoms of meningitis: in Belgium, a whole year can go by diagnosis being made or cases being deelared.We report 5 cases of the most serious form of the illness. namely a hepato-nephritis called“Weils disease”, which can be fatal.Discussion also emphasizes on the seasonal nature of the infection and the occupations most at risk and covers the improved diagnosis through the ELISA technique of an infection whcih often requires the patient to be admitted to intensive care.