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Studies on Restaurant-related Foodborne Illness Outbreaks

This page lists completed EHS-Net food safety studies with a focus on foodborne illness outbreaks and their environmental antecedents.

Read about how EHS-Net’s environmental public health practice work supports CDC’s Winnable Battle on Food Safety. [PDF - 960 KB]

Evaluation of Outbreak and Nonoutbreak Restaurants

Objective: To identify pathogens and contributing factors associated with restaurant-related foodborne illness outbreaks and food-safety differences between outbreak and nonoutbreak restaurants, through systematic environmental evaluations.

Study results: For this study, systematic evaluations were conducted in restaurants in which foodborne illness outbreaks had occurred and in restaurants in which outbreaks had not occurred. Results indicated that Norovirus was the most common foodborne disease agent identified, accounting for 42% of all confirmed foodborne outbreaks during the study period. Handling of food by an infected person or carrier (65%) and bare-hand contact with food (35%) were the most commonly identified contributing factors. Outbreak and nonoutbreak restaurants were similar with respect to many characteristics, but did differ in the presence of a certified kitchen manager (CKM); 32% of outbreak restaurants had a CKM, but 71% of nonoutbreak restaurants had a CKM (OR= 0.2; 95% CI=0.1 to 0.5). CKMs were associated with the absence of bare-hand contact with foods as a contributing factor, fewer norovirus outbreaks, and the absence of outbreaks associated with Clostridium perfringens. Food safety certification of kitchen managers appears to be an important outbreak prevention measure.

Publication: Hedberg CW, Smith SJ, Kirkland E, Radke V, Jones TF, Selman CA, et al. Systematic environmental evaluations to identify food safety differences between outbreak and nonoutbreak restaurants. [PDF - 195 KB] J Food Prot. 2006;69(11):2697-702.

Study findings in plain language: Food Safety Differences Between Restaurants Linked and Not Linked to Outbreaks.

Foodborne Illness Outbreak Study

Objective: To identify contributing factors to foodborne illness outbreaks in food-service facilities and to describe the characteristics, policies and practices of those facilities. Food-service facilities include restaurants, delis, cafeterias, schools, nursing homes, etc.

Study results: Environmental assessments conducted as part of 154 foodborne illness outbreak investigations in food service establishments provided data on a number of establishment characteristics, policies and practices that may serve as potential antecedents to foodborne illness outbreaks. These data are summarized below as preliminary findings.

  • The majority (84%) of the foodservice establishments involved in the outbreaks were complex establishments, meaning a complex food handling process is utilized for one or more foods handled in the establishment. Additionally, 13% were cook serve establishments, and 3% were prep serve establishments.
  • Spanish was the primary language of 58% of food workers but only 41% of managers could speak Spanish.
  • Floor cleaning policies existed in 95% of establishments, but only 37% of these policies were written.
  • Fewer establishments had policies on cleaning of food contact surfaces (88%), cutting boards (89%), and food slicers (72%).
  • More managers (66%) received paid sick leave than workers (35%).
  • The majority (96%) of establishments had hand sinks available in employee restrooms and work areas (94%). However, hands-free operated sinks were rare (restrooms: 4%; work areas: 3%).

Environmental data such as these can inform food safety program action or hypothesis generation regarding antecedents to foodborne illness outbreaks. Systematic collection, analysis, interpretation, and dissemination of environmental data from foodborne disease outbreak investigations can support the overall foodborne disease surveillance system in the United States, strengthening the ability of food-control authorities at all levels of government to formulate food safety action and assess the effectiveness of those actions.

Poster presentation: Delea KC, Selman CA, EHS-Net. Understanding foodborne disease outbreaks using environmental assessment. [PDF - 77 KB] Presented at the Conference on Emerging Infectious Diseases Biannual Meeting; 2008 March 16-19, Atlanta.

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