Urban epidemic of severe leptospirosis in Brazil

Background Leptospirosis has, traditionally, been considered a sporadic rur al disease. We describe a large urban outbreak of leptospirosis. Methods Active surveillance for leptospirosis was established in an infecti ous-disease referral hospital in Salvador, Brazil, between March 10 and Nov 2, 1996. Patients meeting case criteria for severe manifestations of lepto spirosis were recruited into the study. The diagnosis was confirmed in the laboratory with the microagglutination test and identification of leptospir es in blood or urine. Risk factors for death were examined by multivariate analyses. Findings Surveillance identified 326 cases of which 193 (59%) were laborato ry-confirmed (133) or probable (60) cases. Leptospira interrogans serovar c openhageni was isolated from 87% of the cases with positive blood cultures. Most of the cases were adult (mean age 35.9 years [SD 15.9]), and 80% were male. Complications included jaundice (91%), oliguria (35%), and severe an aemia (26%). 50 cases died (case-fatality rate 15%) despite aggressive supp ortive care including dialysis (in 23%). Altered mental status was the stro ngest independent predictor of death (odds ratio 9.12 [95% CI 4.28-20.3]), age over 37 years, renal insufficiency, and respiratory insufficiency were also significant predictors of death. Before admission to hospital, 42% wer e misdiagnosed as having dengue fever in the outpatient clinic; an outbreak of dengue fever was taking place concurrently. Interpretation An epidemic of leptospirosis has become a major urban health problem, associated with high mortality. Diagnostic confusion with dengue fever, another emerging infectious disease with a similar geographic distri bution, prevents timely intervention that could minimise mortality.