In the United States, Salmonella has been isolated from over 31,000 persons during 1979; this figure is more than 60% higher than isolations made 18 years earlier. In Canada, the change from about 5,000 isolations from humans in 1977 to more than 8,000 in 1979 is also approximately a 60% increase, but over an interval of only 3 years. In the U.S. during 1973 – 1978, salmonellosis accounted for 40% of reported cases of foodborne disease and 23% of reported outbreaks of foodborne disease. In Canada during 1973–1975, it accounted for 39% of all reported cases of foodborne disease and 25% of reported outbreaks of foodborne disease. Foods most frequently reported as vehicles of salmonellosis in the U.S. were beef, turkey, homemade ice cream (containing eggs), pork and chicken. Turkey was the most frequently reported vehicle in Canada. Factors usually contributing to these outbreaks (in order of importance) are improper cooling, lapse of a day or more between preparation and serving, inadequate cooking or heat processing, ingestion of contaminated raw ingredients, and cross-contamination. Changes in the relative frequency of isolations of particular serovars sometimes indicate spread of foodborne Salmonella by a particular food or the effectiveness of a control measure. Factors that perpetuate the Salmonella problem are Salmonella-contaminated rendered animal byproducts and contaminated feed, concentrating animals in feed lots and brooding houses, spreading Salmonella during animal slaughtering and processing foods of animal origin, national and international distribution of food and feeds, food preparation and storage practices in foodservice establishments and homes and environmental contamination from animal wastes and other sources.

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