Size and Extent of Foodborne Outbreaks

When two or more people get the same illness from the same contaminated food or drink, the event is called a foodborne outbreak. Illnesses that are not part of outbreaks are called "sporadic." Public health officials investigate outbreaks to control them, so more people do not get sick in the outbreak, and to learn how to prevent similar outbreaks from happening in the future.

The size and scope of a foodborne outbreak can vary based on which pathogen or toxin is involved, how much food is contaminated, where in the food production chain contamination occurs, where the food is served, and how many people eat it. For example:

• Small, local outbreak—A contaminated casserole served at a church supper may cause a small outbreak among church members who know each other.
• Statewide or regional outbreak—A contaminated batch of ground beef sold at several locations of a grocery store chain may lead to illnesses in several counties or even in neighboring states.
• Multistate outbreak—Contaminated produce from one farm may be shipped to grocery stores nationwide and make hundreds of people sick in many states.