After a foodborne outbreak is identified, specific food vehicles may become the focus of an investigation based on the pathogen implicated and past outbreaks linked to the pathogen. For example, Escherichia coli O157:H7 is often linked to leafy greens or ground beef, while Vibrio parahaemolyticus is often linked to oysters. However, in some cases, a novel food vehicle emerges that had not been previously linked to a specific pathogen.

While it is true that some foods have a continuing and repeated pattern of association with outbreaks, over time, these patterns of specific foods associated with outbreaks can change. After a specific food is first linked to a pathogen, that food-pathogen pair may then be observed in future outbreaks as a result of increased focus on that particular food as a potential source for the pathogen or due to increased sampling of that product. This link may also indicate an emerging problem inherent to the production of that food.