Leptospirosis is a zoonosis found worldwide, with an incidence that is approximately 10 times higher in the tropics than in temperate regions. The main reservoir of leptospirosis is the rat and human infection usually results from exposure to infected animal urine or tissues. Only 10% of cases are symptomatic. We present here two confirmed and two probable cases of leptospirosis in a family returning from whitewater rafting in Thailand, illustrating the wide variety of the clinical manifestations of this infection. Two of the patients were hospitalized and presented a probable Jarisch-Herxheimer reaction after initiation of beta-lactam therapy. The two others patients were treated empirically with doxycycline. We discuss here some relevant aspects of the epidemiology, clinical manifestations, therapy and the challenge of an early diagnosis of leptospirosis.