Differentiating leptospirosis from Rickettsial diseases and Q fever: A syndrome-based study in Southern Taiwan.

Leptospirosis, Q fever, scrub typhus, and murine typhus are endemic zoonotic diseases in southern Taiwan that often present as acute undifferentiated febrile illness. We retrospectively compared epidemiological, clinical, laboratory, and outcome characteristics of leptospirosis (n = 41) and rickettsial infections, including Q fever, scrub typhus, and murine typhus (QSM; n = 103), in Kaohsiung City from 2013 to 2024. Leptospirosis occurred mainly during rainy and typhoon seasons and was associated with myalgia, gastrointestinal symptoms, jaundice, conjunctival suffusion, hepatic and renal dysfunction, leukocytosis, elevated C-reactive protein, and higher rates of acute kidney injury and shock. QSM occurred year-round, with eschar characteristic of scrub typhus, while prolonged activated partial thromboplastin time and relative bradycardia were more common in QSM. QSM generally showed a milder clinical course, particularly Q fever. Distinct clinical and seasonal patterns may facilitate early differentiation and risk stratification in endemic areas.