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FOODBORNE ILLNESSES

INTRODUCTION AND EPIDEMIOLOGY

Foodborne illness occurs after consumption of a food contaminated with bacteria, viruses, or protozoans. Outbreaks from contaminated food are often widespread due to advances in modern food logistics. International travel contributes to foodborne illnesses as travelers are exposed to new pathogens and migrants may introduce diseases, making foodborne disease a global public health concern.1

The Centers for Disease Control and Prevention estimates that foodborne diseases affect 9 million Americans each year, leading to 128,000 hospitalizations and 3000 deaths.2,3 Children have the highest frequency of foodborne illness. Viruses are the most common cause of foodborne disease, with the norovirus causing more than half all cases and 26% of all admissions.2 Other viral sources of infection include rotavirus, astrovirus, and enteric adenovirus.

Although less frequent, bacterial causes tend to be more severe, with nontyphoidal Salmonella and Listeria most often resulting in fatality.2,3 Other common bacterial causes of foodborne illness include Clostridium perfringens, Campylobacter spp., Toxoplasma gondii, Shigella, Staphylococcus aureus, and Shiga toxin–producing Escherichia coli (STEC). The most common foods associated with foodborne illness outbreaks from any pathogen reported in the United States are poultry, leafy vegetables, and fruits/nuts.2,3 For further discussion, see Chapter 73, “Disorders Presenting Primarily With Diarrhea.”

PATHOPHYSIOLOGY

There are three basic mechanisms by which microbes cause illness. First, some pathogens such as S. aureus, Bacillus cereus, and Clostridium botulinum (botulism) produce toxins causing illness. These toxins are present in the food before ingestion and result in the rapid onset (1 to 6 hours) of symptoms. Preformed toxins such as staphylococcal enterotoxin stimulate the host immune system to release inflammatory cytokines within the intestine.4 These cytokines trigger the accompanying nausea and vomiting.

The second method involves toxin production after ingestion, which interacts with intestinal epithelium; this occurs with Vibrio, Shigella, and STEC. These cause diarrhea (sometimes bloody) and lower abdominal cramping, with onset at approximately 24 hours after exposure. Some toxins produced by Vibrio and enterotoxigenic E. coli alter chloride and sodium transport across intestinal mucosal surfaces without destroying cells.5 The resulting osmotic gradient produces a large fluid shift into the intestinal lumen, which overwhelms the absorptive capacity of the colon causing watery diarrhea. Other toxins produced disrupt host cell protein production, which causes death of the intestinal epithelium, resulting in bloody diarrhea and extraintestinal symptoms.6

Finally, direct invasion of the intestinal epithelium is a mechanism for the enteric viruses, notably Salmonella, enteroinvasive E. coli, and Campylobacter. These pathogens enter host cells and destroy intestinal epithelium.7 This causes diarrhea due to transient malabsorption that is frequently bloody and accompanied by fever. Illness requires ingestion of just a few pathogens to cause disease. The upper and lower GI symptoms ...

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