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collection, collation, and analysis of data on reports of 

 outbreaks provided to us by state health departments, and the 

 dissemination of those data to appropriate individuals and 

 organizations. In this system, an outbreak is defined as an 

 incident in which 2 or more persons experience a similar illness 

 after ingesting a common food that is epidemiologically 

 implicated as the cause of the illness. A few exceptions exist; 

 for example, one case of ciguatera or scombroid fish poisoning is 

 considered an outbreak. 



Data requested by CDC regarding each outbreak include: 

 number of cases, persons hospitalized, and fatalities; clinical 

 history of ill persons; incubation period and duration of 

 illness; results of epidemiologic investigation, including the 

 source of transmission by epidemiologic evidence; place of 

 preparation of the contaminated item; place where eaten; manner 

 in which the implicated food was marketed; factors, such as 

 improper food handling, which were believed to have contributed 

 to the outbreak; and pertinent laboratory data. Analysis of 

 outbreak data has proved valuable in characterizing the risk of 

 foodborne diseases and documenting the efficacy of regulatory 

 controls developed in response to CDC recommendations. 



The quantity and quality of the data on foodborne outbreaks, 

 however, are limited, and these limitations must be recognized to 

 avoid misinterpretation. The number of outbreaks of foodborne 

 diseases reported by CDC's surveillance system represents only a 

 small fraction of the total number that occur. The likelihood of 

 an outbreak coming to the attention of health authorities varies 

 considerably depending on consumer and physician awareness. For 

 example, large outbreaks, interstate outbreaks, restaurant - 

 associated outbreaks, and outbreaks involving serious illness, 

 hospitalizations, or deaths are more likely to come to the 

 attention of health authorities than are cases of mild illness 

 following a fconily cookout . 



A number of other factors also influence the completeness 

 and representativeness of the data. The quality of the data 

 depends upon the state or local health department's investigative 

 and laboratory capabilities, capabilities that have been severely 

 tested by scarce resources and high demands placed on the public 

 health infrastructure during the past decade. 



The likelihood that the findings will be reported to health 

 officials varies from one locality to another. Thus, these data 

 do not show the absolute incidence of foodborne diseases, and 

 they should not be used to draw conclusions about the relative 

 incidence of foodborne diseases caused by various pathogens. For 

 example, foodborne diseases characterized by short incubation 

 periods, such as those caused by chemicals or staphylococcal 

 enterotoxin, are more likely to be recognized as common- source 

 foodborne disease outbreaks than are those diseases with longer 

 incubation periods, such as hepatitis A. Outbreaks involving 

 less common or more difficult to culture pathogens, such as 

 Bacillus cereus, Escherichia coli, Vibrio parahaemolyticus , 

 Yersinia enterocolitica, or Campylobacter jejuni, are less likely 

 to be confirmed because these organisms are often not considered 

 in clinical, epidemiologic, and laboratory investigations. 

 Pathogens that generally cause mild illness will be 

 underrepresented in the data, while those causing serious 

 illness, such as Clostridium Jbotulinum, are more likely to be 

 identified. Similarly, foods that are served to greater numbers 

 of persons or restaurant- or commercial product-associated 

 outbreaks have a higher likelihood of being detected and 

 reported. 



Because of these factors, the surveillance system is skewed 

 toward more severe diseases, such as botulism and ciguatera, and 

 diseases characterized by mild, rather nonspecific 

 gastrointestinal symptoms are more often underreported. Finally, 



