Outbreaks

The vast majority of reported cases of foodborne illnesses occur as individual or sporadic cases. The origin of most sporadic cases is undetermined. In the United States, where people eat outside the home frequently, most outbreaks (58%) originate from commercial food facilities (FoodNet data). An outbreak is defined as occurring when two or more people experience a similar illness after consuming food from a common source.

Often, a combination of events contributes to an outbreak. For example, food might be left at room temperature for many hours, allowing bacteria to multiply, which is compounded by inadequate cooking, which fails to kill the dangerously elevated bacterial levels.

Outbreaks usually occur when those affected know each other. However, more and more outbreaks are determined by public health staff from unexpected increases in laboratory results for certain strains of bacteria. Outbreak detection and investigation in the United States are primarily handled by local health jurisdictions and are inconsistent from district to district. It is estimated that 1–2% of outbreaks are detected. The outbreak is usually announced through press conferences by the local health jurisdictions.