title: Outbreak of Shiga toxin-producing Escherichia coli (STEC) O157:H7 associated with romaine lettuce consumption, 2011.
abstract: BACKGROUND
  Shiga toxin-producing Escherichia coli (STEC) O157:H7 is the causal agent for more than 96,000 cases of diarrheal illness and 3,200 infection-attributable hospitalizations annually in the United States.
  
  
  METHODS
  We defined a confirmed case as a compatible illness in a person with the outbreak strain during 10/07/2011-11/30/2011. Investigation included hypothesis generation, a case-control study utilizing geographically-matched controls, and a case series investigation. Environmental inspections and tracebacks were conducted.
  
  
  RESULTS
  We identified 58 cases in 10 states; 67% were hospitalized and 6.4% developed hemolytic uremic syndrome. Any romaine consumption was significantly associated with illness (matched Odds Ratio (mOR) = 10.0, 95% Confidence Interval (CI) = 2.1-97.0). Grocery Store Chain A salad bar was significantly associated with illness (mOR = 18.9, 95% CI = 4.5-176.8). Two separate traceback investigations for romaine lettuce converged on Farm A. Case series results indicate that cases (64.9%) were more likely than the FoodNet population (47%) to eat romaine lettuce (p-value = 0.013); 61.3% of cases reported consuming romaine lettuce from the Grocery Store Chain A salad bar.
  
  
  CONCLUSIONS
  This multistate outbreak of STEC O157:H7 infections was associated with consumption of romaine lettuce. Traceback analysis determined that a single common lot of romaine lettuce harvested from Farm A was used to supply Grocery Store Chain A and a university campus linked to a case with the outbreak strain. An investigation at Farm A did not identify the source of contamination. Improved ability to trace produce from the growing fields to the point of consumption will allow more timely prevention and control measures to be implemented.
authors: Epidemic Intelligence Service, Centers for Disease Control and Prevention, Atlanta, Georgia, USA. RSlayton@cdc.gov
authors: Rachel B
authors: RB
authors: Slayton
authors: George
authors: G
authors: Turabelidze
authors: Sarah D
authors: SD
authors: Bennett
authors: Colin A
authors: CA
authors: Schwensohn
authors: Anna Q
authors: AQ
authors: Yaffee
authors: Faisal
authors: F
authors: Khan
authors: Cindy
authors: C
authors: Butler
authors: Eija
authors: E
authors: Trees
authors: Tracy L
authors: TL
authors: Ayers
authors: Marjorie L
authors: ML
authors: Davis
authors: Alison S
authors: AS
authors: Laufer
authors: Stephen
authors: S
authors: Gladbach
authors: Ian
authors: I
authors: Williams
authors: Laura B
authors: LB
authors: Gieraltowski
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015373:Bacterial Typing Techniques; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks; D019453:Escherichia coli O157 / Q000235:genetics / Q000302:isolation & purification*; D005260:Female; D005516:Food Microbiology; D006463:Hemolytic-Uremic Syndrome / Q000453:epidemiology* / Q000382:microbiology / Q000473:pathology; D006801:Humans; D007223:Infant; D018545:Lactuca / Q000382:microbiology*; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D058028:Research Report; D022621:Shiga Toxin / Q000302:isolation & purification*; D014481:United States / Q000453:epidemiology
chemical_list: D022621:Shiga Toxin
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