Submitted to: Archives of Pediatrics and Adolescent Medicine
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/20/2008
Publication Date: 1/1/2009
Publication URL: http://hdl.handle.net/10113/28293
Citation: Goode, B., O'Reilly, C., Dunn, J., Fullerton, K., Smith, S., Ghneim, G., Keen, J., Durso, L.M., Davies, M., Montgomery, S. 2009. Outbreak of Escherichia coli O157:H7 Infections After Petting Zoo Visits, North Carolina State Fair, October-November 2004. Archives of Pediatrics and Adolescent Medicine. 163(1):42-48. Interpretive Summary: This paper describes the investigation of an outbreak of Escherichia coli O157:H7 at the 2004 North Carolina State Fair. There were a total of 108 cases identified as part of this investigation, including 41 cases with laboratory-confirmed illness. Environmental samples from a specific petting zoo area were culture-positive for E. coli O157:H7 and had a DNA fingerprint which was indistinguishable from the DNA fingerprint of the E. coli O157:H7 isolated from sick humans. Visiting the contaminated petting zoo was associated with illness, and children 5 years or younger who had visited the implicated petting zoo were more likely to get sick if they had contact with animal manure, or if they displayed hand-to-mouth behaviors. Use of alcohol-based hand sanitizing gels was not protective; however, knowledge about the risks of getting sick from the animals was protective. Recommendations for preventing future outbreaks include using physical barriers to separate visitors from animal manure, education, and appropriate hand hygiene practices.
Technical Abstract: Objectives: To identify cases, describe the outbreak, implement control measures, and identify factors associated with infection or protection from infection, including contact with animals and hand hygiene practices. Design: Case finding, a case-control study of 45 cases and 188 controls, environmental investigation, and molecular subtyping of clinical and environmental Escherichia coli O157:H7 isolates. Setting: The 2004 North Carolina State Fair. Participants: Case patients were fair visitors who had laboratory-confirmed E. coli O157 infections, hemolytic uremic syndrome (HUS) diagnoses, or bloody diarrheal illnesses. Control subjects were recruited from a randomized list of persons who had purchased fair tickets online. Environmental samples from the fairgrounds were obtained from locations that had held animals during the fair. Main Exposure: Visiting a petting zoo. Main Outcome Measures: Case finding: Summary descriptive statistics of suspected, probable, or confirmed E. coli O157:H7 infections, signs, symptoms, and HUS. Environmental investigation: E. coli O157:H7 isolates, pulsed-field gel electrophoresis patterns, and spatial distribution of source locations. Case-control study: Odds ratios (ORs) comparing reported fair-related activities, hygiene practices, and zoonotic disease knowledge with outcome. Results: A total of 108 case patients were ascertained, including 41 with laboratory-confirmed illness and 15 who experienced HUS. Forth-five case patients and 188 controls were enrolled in the case-control study. Visits to a petting zoo having substantial environmental E. coli O157:H7 contamination were associated with illness (age-adjusted OR, 8.2; 95% confidence interval [CI], 3.3-20.3). Among children 5 years or younger who had visited the implicated petting zoo, contact with animal manure (OR, 6.9; 95% CI, 2.2-21.9) and hand-to-mouth behaviors (OR, 10.6; 95% CI, 2.0-55.0) were associated with illness. Reported hand hygiene practices did not differ significantly (OR, 1.8; 95% CI, 0.3-9.5). Reported awareness of the risk for zoonotic disease was protective (OR, 0.1; 95% CI, 0.03-0.5). Environmental samples from the petting zoo implicated in the case-control study yielded E. coli O157:H7, with indistinguishable pulsed-field gel electrophoresis patterns from the predominant strain. Conclusion: We describe one of the largest petting zoo outbreaks of E. coli O157:H7 to date. Persons became infected after contact with manure and engaging in hand-to-mouth behaviors in a petting zoo having substantial E. coli O157:H7 contamination. Use of alcohol-based hand-sanitizing gels was not protective, although knowledge of the risk for zoonotic infection was protective. Future investigations in similar outbreaks should assess risks for infection and protective measures (e.g., physical barriers separating visitors from animal manure, education, and appropriate hand hygiene practices).