Outbreak Investigation

What It Means

An outbreak investigation is a systematic, multi-agency process conducted to identify the source of a foodborne illness outbreak, determine the scope of the problem, and implement measures to prevent additional cases. In the United States, outbreak investigations are coordinated among the CDC, FDA, USDA, and state and local health departments. The investigation process typically begins when surveillance systems detect an unusual cluster of illnesses. PulseNet, the national molecular subtyping network for foodborne disease surveillance maintained by the CDC, uses DNA fingerprinting of pathogens to identify clusters of related infections across different states. Once an outbreak is identified, investigators work to determine the food source through several methods: interviewing sick individuals about what they ate in the days before becoming ill, comparing the eating habits of sick individuals with those of healthy controls (case-control studies), trace-back investigations to track contaminated food from the point of sale back through the distribution chain to the source, and environmental assessments at processing facilities or farms. When the source food is identified, the FDA or USDA works with the responsible company to initiate a recall. Outbreak investigations can be complex and time-consuming, often taking weeks or months to identify the source. Meanwhile, public warnings may be issued advising consumers to avoid certain foods. The results of outbreak investigations contribute to the body of food safety knowledge and inform preventive measures.