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Am Fam Physician. 2004;70(5):981-985

In collaboration with the American Medical Association, American Nurses Association-American Nurse Foundation, the U.S. Food and Drug Administration’s Center for Food Safety and Nutrition, and the U.S. Department of Agriculture’s Food Safety and Inspection Service, the Centers for Disease Control and Prevention (CDC) has issued new recommendations for diagnosing, managing, and reporting foodborne illnesses. The report focuses on recognizing suspicious symptoms, disease clusters, and etiologic agents, and reporting cases of foodborne illness to public health authorities. Summary tables and charts, references, and resources for health care professionals are provided. Patient scenarios, clinical vignettes, and a continuing medical education component also are included. The full report is available in the April 16, 2004, issue of the Morbidity and Mortality Weekly Report: Recommendations and Rationale and online at

Clinical Considerations

The CDC estimates that 76 million persons get sick, 300,000 are hospitalized, and 5,000 die as a result of food-borne illnesses per year. Primarily very young, elderly, and immunocompromised patients are affected. Food-borne illness can be caused by microorganisms and their toxins, marine organisms and their toxins, fungi, and their related toxins, and chemical contaminants. Foods that have been linked to outbreaks include milk, shellfish, unpasteurized apple cider, raw and undercooked eggs, fish, raspberries, strawberries, and ready-to-eat meats. The accompanying table lists etiologic agents to consider for various manifestations of foodborne illness.

Clinical presentationPotential food-related agents to consider
Gastroenteritis (vomiting as primary symptom; fever or diarrhea also may be presentViral gastroenteritis, most commonly rotavirus in an infant or norovirus and other caliciviruses in an older child or adult; or food poisoning caused by preformed toxins (e.g., vomitoxin, Staphylococcus aureus toxin, Bacillus cereus toxin) and heavy metals
Noninflammatory diarrhea (acute watery diarrhea without fever or dysentery; some patients may presentwith fever)*Can be caused by virtually all enteric pathogens (bacterial, viral, parasitic) but is a classic symptom of enterotoxigenic Escherichia coli, Giardia, Vibrio cholerae, enteric viruses (astroviruses, noroviruses, and other calciviruses, enteric adenovirus, rotavirus), Cryptosporidium, Cyclospora cayetanensis
Inflammatory diarrhea (invasive gastroenteritis; grossly bloody stool and fever may be present)†Shigella species, Campylobacter species, Salmonella species, enteroinvasive E. coli, enterohemorrhagic E. coli, E. coli O157:H7, Vibrio parahaemolyticus, Yersinia enterocolitica, Entamoeba histolytica
Persistent diarrhea (lasting at least 14 days)Prolonged illness should prompt examination for parasites, particularly in travelers to mountainous or other areas where untreated water is consumed. Consider Cyclospora cayetanensis, Cryptosporidium, Entamoeba histolytica, and Giardia lamblia.
Neurologic manifestations (e.g., paresthesias, respiratory depression, bronchospasm, cranial nerve palsies)Botulism (Clostridium botulinum toxin), organophosphate pesticides, thallium poisoning, scombroid fish poisoning (histamine, saurian), ciguatera fish poisoning (ciguatoxin), tetraodon fish poisoning (tetraodontoxin), neurotoxic shellfish poisoning (brevetoxin), paralytic shellfish poisoning (saxitoxin), amnesic shellfish poisoning (domoic acid), mushroom poisoning, Guillain-Barré syndrome (associated with infectious diarrhea caused by Campylobacter jejuni)
Systemic illness (e.g., fever, weakness, arthritis, jaundice)Listeria monocytogenes, Brucella species, Trichinella spiralis, Toxoplasma gondii, Vibrio vulnificus, hepatitis A and E viruses, Salmonella typhi and Salmonella paratyphi, amebic liver abscess

Recognizing Foodborne Illness

Patients with foodborne illnesses typically present with gastrointestinal tract symptoms (e.g., vomiting, diarrhea, abdominal pain), but nonspecific symptoms and neurologic symptoms also may occur. Important clues to determining the etiology of a foodborne disease are the incubation period, duration of the illness, predominant clinical symptoms, and population involved in the outbreak.


Establishing a diagnosis can be difficult, particularly in patients with persistent or chronic diarrhea, those with severe abdominal pain, and those who have an underlying disease process. Because viral syndrome has a similar presentation, it must be excluded before suspecting food-borne illness. Fever, diarrhea, and abdominal cramps can be present or absent in viral or foodborne illness, so they are not good indicators. The absence of myalgias or arthralgias would make a viral syndrome less likely. Foodborne illnesses that target the neurologic system tend to cause paresthesias, weakness, and paralysis. The presence of dysentery (bloody diarrhea) also is more indicative of a foodborne illness, particularly if it is early in the course of the illness.

If any of the following signs and symptoms occur in patients, alone or in combination, laboratory testing may provide diagnostic clues (attention should be given to very young, elderly, or immunocompromised patients):

  • Bloody diarrhea

  • Diarrhea leading to dehydration

  • Fever

  • Prolonged diarrhea (three or more unformed stools per day, persisting several days)

  • Neurologic involvement, such as paresthesias, motor weakness, cranial nerve palsies

  • Sudden onset of nausea, vomiting, diarrhea

  • Severe abdominal pain

Clinical Microbiology Testing

Stool cultures are indicated if the patient is immunocompromised, febrile, has bloody diarrhea, has severe abdominal pain, or if the illness is clinically severe or persistent. Stool cultures also are recommended if the fecal leukocyte count is high. Stool examination for parasites generally is indicated for patients with suggestive travel histories, those who are immunocompromised, those who suffer chronic or persistent diarrhea, or when the diarrheal illness is unresponsive to appropriate antimicrobial therapy. Stool examination for parasites also is recommended for gastrointestinal tract illnesses that appear to have a long incubation period. Blood cultures should be obtained when bacteremia or systemic infection is suspected.


Selection of appropriate treatment depends on identification of the responsible pathogen (if possible) and determining if specific therapy is available. Many episodes of acute gastroenteritis are self-limiting and require fluid replacement and supportive care. Oral rehydration is indicated for patients who are mildly to moderately dehydrated; intravenous therapy may be required for more severe dehydration. Routine use of antidiarrheal agents is not recommended because many of these agents potentially have serious adverse effects in infants and young children. Antimicrobial therapy should be based on clinical signs and symptoms; the organism detected in clinical specimens; antimicrobial susceptibility tests; and appropriateness of antibiotic treatment (some enteric bacterial infections are best not treated).

Surveillance and Reporting of Foodborne Illness

Health care professionals may suspect foodborne illness because of the organism involved or other available information, such as several ill patients who have eaten the same food. Foodborne disease reporting is important for disease prevention and control. More accurate assessments of the burden of foodborne illness in the community occur when physicians and other health professionals report these illnesses to the local and state health departments. These reports may help the health department identify an outbreak in the community, improving early identification and removal of contaminated products from the commercial market.

Typically, the appropriate procedure for health care professionals to follow in reporting foodborne illnesses is to contact the local or state health department whenever they identify a specific notifiable foodborne disease. However, it is often unclear if a patient has a foodborne illness before diagnostic testing, so health care professionals also should report potential foodborne illnesses, such as when two or more patients present with a similar illness that may have resulted from the ingestion of a common food. Local health departments will then report the illnesses to the state health departments, where it is determined if further investigation is necessary.

Coverage of guidelines from other organizations does not imply endorsement by AFP or the AAFP.

This series is coordinated by Michael J. Arnold, MD, associate medical editor.

A collection of Practice Guidelines published in AFP is available at

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