title: Hamburger-associated Escherichia coli O157:H7 infection in Las Vegas: a hidden epidemic.
abstract: OBJECTIVE
  This study sought to determine whether a multistate fast food hamburger-associated outbreak of Escherichia coli O157:H7 infection involved Las Vegas residents as well and, if so, why public health officials had not detected it.
  
  
  METHODS
  A matched case-control study was conducted among persons with bloody diarrhea and their healthy meal companions. Hamburger production, distribution, and cooking methods were reviewed. Unused hamburger patties were cultured, and E. coli O157:H7 isolates were characterized. Local laboratory stool culture practices were reviewed.
  
  
  RESULTS
  Fifty-eight cases of bloody diarrhea were identified. Illness was associated with eating regular hamburgers (matched odds ratio [OR] = 9.0, 95% confidence interval [CI] = 1.02,433.4), but 25% of ill persons reported eating only jumbo hamburgers. Regular and jumbo hamburger patties yielded E. coli O157:H7 indistinguishable from the lone clinical isolate. No local laboratory cultured routinely for E. coli O157:H7 until after the outbreak.
  
  
  CONCLUSIONS
  A large outbreak of E. coli O157:H7 infections escaped timely notice in Las Vegas because local laboratories did not culture for this pathogen. Health officials should encourage laboratories to screen at least all bloody stools on sorbitol-MacConkey medium.
authors.affiliation: National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Ga 30333, USA.
authors.forename: P R
authors.initials: PR
authors.lastname: Cieslak
authors.forename: S J
authors.initials: SJ
authors.lastname: Noble
authors.forename: D J
authors.initials: DJ
authors.lastname: Maxson
authors.forename: L C
authors.initials: LC
authors.lastname: Empey
authors.forename: O
authors.initials: O
authors.lastname: Ravenholt
authors.forename: G
authors.initials: G
authors.lastname: Legarza
authors.forename: J
authors.initials: J
authors.lastname: Tuttle
authors.forename: M P
authors.initials: MP
authors.lastname: Doyle
authors.forename: T J
authors.initials: TJ
authors.lastname: Barrett
authors.forename: J G
authors.initials: JG
authors.lastname: Wells
authors.forename: A M
authors.initials: AM
authors.lastname: McNamara
authors.forename: P M
authors.initials: PM
authors.lastname: Griffin
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D016022:Case-Control Studies; D002417:Cattle; D002648:Child; D002675:Child, Preschool; D003296:Cooking; D003967:Diarrhea / Q000382:microbiology*; D004196:Disease Outbreaks; D004927:Escherichia coli Infections / Q000453:epidemiology* / Q000382:microbiology; D019453:Escherichia coli O157 / Q000302:isolation & purification* / Q000472:pathogenicity; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008460:Meat / Q000382:microbiology / Q000506:poisoning*; D008875:Middle Aged; D009505:Nevada / Q000453:epidemiology; D012147:Restaurants