Some known pathogens have only recently been shown to be predominantly foodborne, such as Listeria monocytogenes and Campylobacter jejuni . Traditionally, the food implicated in a foodborne outbreak was undercooked meat, poultry, or seafood, or unpasteurized milk. Imported raspberries contaminated with Cyclospora caused an epidemic in the United States in 1996. Norwalk-like viruses, which appear to have a human reservoir, have contaminated oysters harvested from pristine waters. The new food vehicles of disease share several features.
Contamination typically occurs early in the production process, rather than just before consumption.
Because of consumer demand and the global food market, ingredients from many countries may be combined in a single dish, which makes the specific source of contamination difficult to trace. 6 Campylobacter spp. Many diseases of foodborne origin have a long incubation period before symptoms develop. This time lag makes it difficult to trace problems back to the specific cause of illness. Several meals may have been eaten before the foodborne disease symptoms appeared.