Infectious dose is the amount of a disease-causing microorganism that must enter a host to produce infection. In food safety, it helps explain why some pathogens can cause illness after exposure to relatively small numbers of organisms, while others generally require a larger exposure. There is no single infectious-dose value that applies to all pathogens or all people.
Some pathogens, including certain Shiga toxin-producing Escherichia coli strains and norovirus, can cause illness at relatively low exposure levels. Other organisms may require a greater dose under particular conditions. These are broad tendencies, not safe thresholds for food handling: even a small contamination event can be significant.
An infectious dose refers to exposure to viable organisms capable of establishing infection. A toxin-mediated illness can occur when a person consumes a toxin that was produced in food before eating. In that case, the amount of toxin matters, and killing the organism during cooking may not destroy a heat-stable toxin that has already formed.
Never use a presumed infectious-dose threshold to decide that contaminated food is acceptable. Prevent contamination, maintain safe time-temperature controls, cook foods using validated procedures, prevent cross-contamination and discard food when required by the food-safety plan or regulator.
Chef’s tip: The infectious dose is a scientific concept for understanding risk, not a target or tolerance for kitchen operations. Treat contamination prevention and hygiene as essential even when the amount of contamination is unknown or appears small.
This term is one of hundreds covered in depth across OCS courses, learning paths, and 1-on-1 coaching with Chef Eric.
