Foodborne illnesses are classified into three main categories based on the mechanism of pathogenesis. Foodborne infections occur when live pathogenic microorganisms are ingested, colonize the gastrointestinal tract, and cause illness through invasion or toxin production inside the host. Common bacterial infections include Salmonella (non-typhoidal), Campylobacter jejuni, and pathogenic Escherichia coli. Viral infections such as norovirus and hepatitis A are also classified as infections. Incubation periods are typically 12-72 hours, and symptoms include diarrhea, fever, abdominal cramps, and vomiting, lasting several days.
Foodborne intoxications result from ingestion of pre-formed toxins produced by microorganisms in the food before consumption. Clostridium botulinum produces botulinum neurotoxin in improperly canned low-acid foods, causing a severe paralysis syndrome with incubation of 12-36 hours. Staphylococcus aureus enterotoxin is heat-stable and causes rapid-onset (1-6 hours) vomiting and diarrhea. Bacillus cereus emetic toxin (cereulide) is pre-formed in rice and pasta dishes. Because the toxin is already present, cooking the food after toxin formation does not eliminate the illness risk.
Toxicoinfections fall between infections and intoxications. The pathogen is ingested and then produces toxin in the gastrointestinal tract. Clostridium perfringens type A produces enterotoxin during sporulation in the small intestine, causing watery diarrhea 8-16 hours after ingestion. Bacillus cereus diarrheal type produces enterotoxins in the gut. Vibrio cholerae and enterotoxigenic E. coli (ETEC) also produce enterotoxins in the intestine after colonization.
Outbreak investigation relies on distinguishing these mechanisms. Short incubation periods with vomiting suggest intoxication, while longer incubation with fever indicates infection. Laboratory confirmation requires detection of the pathogen in stool (for infections and toxicoinfections) or toxin in food (for intoxications). Surveillance systems such as PulseNet (PFGE and WGS typing) track outbreak strains. Prevention strategies differ accordingly: preventing contamination and growth for intoxications, versus adequate cooking and prevention of cross-contamination for infections. Classic foodborne infections include Salmonella and Campylobacter, while intoxication is exemplified by Clostridium botulinum. Norovirus and Hepatitis A represent viral foodborne infections with distinct epidemiology.
