Leptospirosis is associated with severity, increased resource utilization, and mortality among acute febrile illnesses from Karnataka, Southwestern India

Introduction: Acute febrile illness (AFI) is prevalent in tropical regions, with varying etiologies across South Asia. Limited data exists regarding its epidemiology. We aimed to determine the etiology, severity, organ dysfunction, and fatality rate of AFI. Materials and Methods: This prospective cross-sectional study was conducted at a tertiary care hospital in Southwestern India from September 2016 to August 2018. Hospitalized adults aged >18 years with fever (3–14 days) and no infection foci were included. Patients with co-infections, immunocompromised status, chronic kidney disease, chronic obstructive pulmonary disease, or chronic liver disease were excluded. Severity was assessed using Sequential Organ Failure Assessment (SOFA) score (≥2 indicating severe illness). Results: Among 314 patients, 66.8% were male. Etiologies included undifferentiated fever (38.5%), dengue (33.1%), scrub typhus (10.2%), leptospirosis (7.6%), malaria (5.1%), and alternate diagnoses (6.4%), with seasonal peaks during monsoon (June to October). Severe illness (SOFA ≥2) was noted in 62.4% of cases. Fatality was 3.2%, with 60% due to undifferentiated fever and 40% due to leptospirosis-associated multi-organ dysfunction. Conclusion: In this study of acute febrile illness (AFI), at a tertiary care hospital in Manipal, Karnataka, India, etiologies were dengue, scrub typhus, leptospirosis, and malaria. Among these, leptospirosis was associated with the highest median SOFA score, severe hepatorenal and cardiopulmonary dysfunction, required intensive support (inotropes, mechanical ventilation, and hemodialysis), and had the highest fatality rate. Limitations include serological diagnosis of some cases of AFI, lack of convalescent serology in undifferentiated cases, and potential referral bias inherent to a tertiary care hospital.