title: Urban epidemic of severe leptospirosis in Brazil. Salvador Leptospirosis Study Group.
abstract: BACKGROUND
  Leptospirosis has, traditionally, been considered a sporadic rural disease. We describe a large urban outbreak of leptospirosis.
  
  
  METHODS
  Active surveillance for leptospirosis was established in an infectious-disease referral hospital in Salvador, Brazil, between March 10 and Nov 2, 1996. Patients meeting case criteria for severe manifestations of leptospirosis were recruited into the study. The diagnosis was confirmed in the laboratory with the microagglutination test and identification of leptospires in blood or urine. Risk factors for death were examined by multivariate analyses.
  
  
  RESULTS
  Surveillance identified 326 cases of which 193 (59%) were laboratory-confirmed (133) or probable (60) cases. Leptospira interrogans serovar copenhageni 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 anaemia (26%). 50 cases died (case-fatality rate 15%) despite aggressive supportive care including dialysis (in 23%). Altered mental status was the strongest 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% were misdiagnosed as having dengue fever in the outpatient clinic; an outbreak of dengue fever was taking place concurrently.
  
  
  CONCLUSIONS
  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 distribution, prevents timely intervention that could minimise mortality.
authors.affiliation: Gonçalo Moniz Research Centre, Oswaldo Cruz Foundation, Brazilian Ministry of Health, Salvador. albertko@cpunet.com.br
authors.forename: A I
authors.initials: AI
authors.lastname: Ko
authors.forename: M
authors.initials: M
authors.lastname: Galvão Reis
authors.forename: C M
authors.initials: CM
authors.lastname: Ribeiro Dourado
authors.forename: W D
authors.initials: WD
authors.lastname: Johnson
authors.forename: L W
authors.initials: LW
authors.lastname: Riley
mesh_terms: D000328:Adult; D001938:Brazil / Q000453:epidemiology; D003715:Dengue / Q000175:diagnosis; D003937:Diagnosis, Differential; D004196:Disease Outbreaks / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D007921:Leptospira interrogans / Q000302:isolation & purification; D008297:Male; D011159:Population Surveillance; D014504:Urban Health / Q000706:statistics & numerical data*; D014895:Weil Disease / Q000175:diagnosis / Q000453:epidemiology*