When history repeats: leptospirosis as a marker of climate change and urban health inequity

Introduction Leptospirosis is a zoonotic spirochetal infection classically associated with tropical or travel-related exposure, but it is increasingly recognized in urban settings, particularly among people experiencing homelessness. Case presentation We describe a 42-year-old man with alcohol use disorder and unstable housing who presented with fever, bilateral leg pain, and diarrhea, with laboratory findings showing thrombocytopenia, azotemia, hyperbilirubinemia, transaminitis, and elevated creatine phosphokinase. He left against medical advice, then returned the next day with worsening jaundice, dark urine, and emesis. Polymerase chain reaction testing confirmed Leptospira infection, and he improved with targeted antimicrobial and supportive therapy. Conclusion This case highlights the diagnostic challenge of leptospirosis, whose nonspecific early presentation can resemble sepsis or drug-induced liver injury, and underscores its rising incidence in temperate urban centers such as New York City (NYC), where housing instability, rodent exposure, and limited healthcare access disproportionately affect vulnerable populations. Clinicians should maintain a high index of suspicion for leptospirosis in patients with compatible symptoms and relevant social history, as early recognition is critical to reducing morbidity and mortality.