Report of Weil's disease with a fatal course triggered by Jarisch-Herxheimer reaction.

Leptospirosis, a zoonotic disease characterized by a spectrum of influenza-like symptoms, can manifest as severe cases so called Weil's disease. Early diagnosis and treatment are crucial to avoid the potentially fatal course of the disease. Within 24 hours of the initial administration of antibiotics, patients may experience the Jarisch-Herxheimer reaction (JHR), characterized by chills, fever, hypotension, and impaired consciousness. The Okinawa Prefecture, where our hospital is situated, boasts the highest incidence rate of leptospirosis among all regions in Japan. This reports our encounter with the initial leptospirosis case after a period of 16 years within the Okinawa Prefecture. This case exhibited JHR and required the utilization of noradrenaline (NA). Despite evidence indicating that JHR does not correlate with mortality, we contend that diagnosis of Weil's disease necessitates admission to an intensive care unit (ICU) and vigilant monitoring for JHR, as it may result in impairment of general condition and fatal outcome, as observed in our case.