Confirming a Diagnosis of Foodborne Illness

Both consumers and food industry interests benefit from being fully informed about the true nature of foodborne illnesses. The complex realities of foodborne illnesses demand that formal medical insight and study is needed to determine the type of outbreak being dealt with at any given time and place. Still, it can be of benefit for any stakeholder in the food industry to learn more about these differing illnesses and their effects on consumers.

For example, just within the realm of bacterial outbreaks, incubation times can range from a few hours to a few months and symptoms can range from fevers and headaches to severe abdominal pain and paralysis, depending on the type of bacteria. The following graph from the CDC* describes incubation periods, symptoms, and other information about foodborne illnesses for a general audience.

 

Table B-1. Guidelines for confirmation of foodborne-disease outbreaks (Bacterial)
Etiologic agent Incubation period Clinical syndrome Confirmation
Bacillus cereus – Vomiting toxin 1-6 hrs Vomiting; some patients with diarrhea; fever uncommon Isolation of organism from stool of two or more ill persons and not from stool of control patients
OR
Isolation of 105 organisms/g from epidemiologically implicated food, provided specimen is properly handled
Bacillus cereus – Diarrheal toxin 6-24 hrs Diarrhea, abdominal cramps, and vomiting in some patients; fever uncommon Isolation of organism from stool of two or more ill persons and not from stool of control patients
OR
Isolation of 105 organisms/g from epidemiologically implicated food, provided specimen is properly handled
Brucella Several days to several mos; usually >30 days Weakness, fever, headache, sweats, chills, arthralgia, weight loss, splenomegaly Two or more ill persons and isolation of organism in culture of blood or bone marrow; greater than fourfold increase in standard agglutination titer (SAT) over several wks, or single SAT 1:160 in person who has compatible clinical symptoms and history of exposure
Campylobacter jejuni/coli 2-10 days; usually 2-5 days Diarrhea (often bloody), abdominal pain, fever Isolation of organism from clinical specimens from two or more ill persons
OR
Isolation of organism from epidemiologically implicated food
Clostridium botulinum 2 hrs-8 days; usually 12-48 hrs Illness of variable severity; common symptoms are diplopia, blurred vision, and bulbar weakness; paralysis, which is usually descending and bilateral, might progress rapidly Detection of botulinum toxin in serum, stool, gastric contents, or implicated food
OR
Isolation of organism from stool or intestine
Clostridium perfringens 6-24 hrs Diarrhea, abdominal cramps; vomiting and fever uncommon Isolation of 106 organisms/g from stool of two or more ill persons, provided specimen is properly handled.
OR
Demonstration of enterotoxin in the stool of two or more ill persons
OR
Isolation of 105 organisms/g from epidemiologically implicated food, provided specimen is properly handled
Escherichia coli – Enterohemorrhagic (E. coli O157:H7 and others) 1-10 days; usually 3-4 days Diarrhea (often bloody), abdominal cramps (often severe), little or no fever Isolation of E. coli O157:H7 or other Shiga-like toxin-producing E. coli from clinical specimen from two or more ill persons
OR
Isolation of E. coli O157:H7 or other Shiga-like toxin-producing E. coli from epidemiologically implicated food
Escherichia coli – Enterotoxigenic (ETEC) 6-48 hrs Diarrhea, abdominal cramps, nausea; vomiting and fever less common Isolation of organism of same serotype, demonstrated to produce heat-stable (ST) and/or heat-labile (LT) enterotoxin, from stool of two or more ill persons
Escherichia coli – Enteropathogenic (EPEC) Variable Diarrhea, fever, abdominal cramps Isolation of organism of same enteropathogenic serotype from stool of two or more ill persons
Escherichia coli – Enteroinvasive (EIEC) Variable Diarrhea (might be bloody), fever, abdominal cramps Isolation of same enteroinvasive serotype from stool of two or more ill persons
Listeria monocytogenes – Invasive disease 2-6 wks Meningitis, neonatal sepsis, fever Isolation of organism from normally sterile site
Listeria monocytogenes – Diarrheal disease Unknown Diarrhea, abdominal cramps, fever Isolation of organism of same serotype from stool of two or more ill persons exposed to food that is epidemiologically implicated or from which organism of same serotype has been isolated
Nontyphoidal Salmonella 6 hrs-10 days; usually 6-48 hrs Diarrhea, often with fever and abdominal cramps Isolation of organism of same serotype from clinical specimens from two or more ill persons
OR
Isolation of organism from epidemiologically implicated food
Salmonella Typhi 3-60 days; usually 7-14 days Fever, anorexia, malaise, headache, and myalgia; sometimes diarrhea or constipation Isolation of organism from clinical specimens from two or more ill persons
OR
Isolation of organism from epidemiologically implicated food
Shigella spp. 12 hrs-6 days; usually 2-4 days Diarrhea (often bloody), often accompanied by fever and abdominal cramps Isolation of organism of same serotype from clinical specimens from two or more ill persons
OR
Isolation of organism from epidemiologically implicated food
Staphylococcus aureus 30 min-8 hrs; usually 2-4 hrs Vomiting, diarrhea Isolation of organism of same phage type from stool or vomitus of two or more ill persons
OR
Detection of enterotoxin in epidemiologically implicated food
OR
Isolation of 105 organisms/g from epidemiologically implicated food, provided specimen is properly handled
Streptococcus, group A 1-4 days Fever, pharyngitis, scarlet fever, upper respiratory infection Isolation of organism of same M- or T-type from throats of two or more ill persons
OR
Isolation of organism of same M- or T-type from epidemiologically implicated food
Vibrio cholerae – O1 or O139 1-5 days Watery diarrhea, often accompanied by vomiting Isolation of toxigenic organism from stool or vomitus of two or more ill persons
OR
Significant rise in vibriocidal, bacterial-agglutinating, or antitoxin antibodies in acute- and early convalescent-phase sera among persons not recently immunized
OR
Isolation of toxigenic organism from epidemiologically implicated food
Vibrio cholerae – non-O1 and non-O139 1-5 days Watery diarrhea Isolation of organism of same serotype from stool of two or more ill persons
Vibrio parahaemolyticus 4-30 hrs Diarrhea Isolation of Kanagawa-positive organism from stool of two or more ill persons
OR
Isolation of 105 Kanagawa-positive organisms/g from epidemiologically implicated food, provided specimen is properly handled
Yersinia enterocolitica 1-10 days; usually 4-6 days Diarrhea, abdominal pain (often severe) Isolation of organism from clinical specimen from two or more ill persons
OR
Isolation of pathogenic strain of organism from epidemiologically implicated food
Table B-2. Guidelines for confirmation of foodborne-disease outbreaks (Chemical)
Etiologic Agent Incubation Period Clinical Syndrome Confirmation
Marine toxins – Ciguatoxin 1-48 hrs; usually 2-8 hrs Usually gastrointestinal symptoms followed by neurologic symptoms(including paresthesia of lips, tongue, throat, or extremities) and reversal of hot and cold sensation Demonstration of ciguatoxin in epidemiologically implicated fish
OR
Clinical syndrome among persons who have eaten a type of fish previously associated with ciguatera fish poisoning (e.g., snapper, grouper, or barracuda)
Marine toxins – Scombroid toxin (histamine) 1 min-3 hrs; usually <1 hr Flushing, dizziness, burning of mouth and throat, headache, gastrointestinal symptoms, urticaria, and generalized pruritis Demonstration of histamine in epidemiologically implicated fish
OR
Clinical syndrome among persons who have eaten a type of fish previously associated with histamine fish poisoning (e.g., mahi-mahi or fish of order Scomboidei)
Marine toxins – Paralytic or neurotoxic shellfish poison 30 min-3 hrs Paresthesia of lips, mouth or face, and extremities; intestinal symptoms or weakness, including respiratory difficulty Detection of toxin in epidemiologically implicated food
OR
Detection of large numbers of shellfish-poisoning-associated species of dinoflagellates in water from which epidemiologically implicated mollusks are gathered
Marine toxins – Puffer fish, tetrodotoxin 10 min-3 hrs; usually 10-45 min Paresthesia of lips, tongue, face, or extremities, often following numbness; loss of proprioception or floating sensations Demonstration of tetrodotoxin in epidemiologically implicated fish
OR
Clinical syndrome among persons who have eaten puffer fish
Heavy metals (Antimony, Cadmium, Copper, Iron, Tin, Zinc) 5 min-8 hrs; usually <1 hr Vomiting, often metallic taste Demonstration of high concentration of metal in epidemiologically implicated food
Monosodium glutamate (MSG) 3 min-2 hrs; usually <1 hr Burning sensation in chest, neck, abdomen, or extremities; sensation of lightness and pressure over face or heavy feeling in chest Clinical syndrome among persons who have eaten food containing MSG (e.g., usually 1.5 g MSG)
Mushroom toxins – Shorter-acting toxins (Muscimol, Muscarine, Psilocybin, Coprinus artrementaris, Ibotenic acid) 2 hrs Usually vomiting and diarrhea, other symptoms differ with toxin

  • Confusion, visual disturbance
  • Salivation, diaphoresis
  • Hallucinations
  • Disulfiram-like reaction
  • Confusion, visual disturbance
Clinical syndrome among persons who have eaten mushroom identified as toxic type
OR
Demonstration of toxin in epidemiologically implicated mushroom or food containing mushroom
Mushroom toxins – Longer-acting toxins (e.g., Amanita spp.) 6-24 hrs Diarrhea and abdominal cramps for 24 hrs followed by hepatic and renal failure Clinical syndrome among persons who have eaten mushroom identified as toxic type
OR
Demonstration of toxin in epidemiologically implicated mushroom or food containing mushrooms
Table B-4. Guidelines for confirmation of foodborne-disease outbreaks (Viral)
Etiologic Agent Incubation Period Clinical Syndrome Confirmation
Hepatitis A 15-50 days; median: 28 days Jaundice, dark urine, fatigue, anorexia, nausea Detection of immunoglobulin M antibody to hepatitis A virus (IgM anti-HAV) in serum from two or more persons who consumed epidemiologically implicated food
Norovirus (NoV) 12-48 hrs (median 33 hours) Diarrhea, vomiting, nausea, abdominal cramps, low-grade fever Detection of viral RNA in at least two bulk stool or vomitus specimens by real-time or conventional reverse transcriptase-polymerase chain reaction (RT-PCR)
OR
Visualization of viruses (NoV) with characteristic morphology by electron microscopy in at least two or more bulk stool or vomitus specimens
OR
Two or more stools positive by commercial enzyme immunoassay (EIA)
Astrovirus 12-48 hrs Diarrhea, vomiting, nausea, abdominal cramps, low-grade fever Detection of viral RNA in at least two bulk stool or vomitus specimens by real-time or conventional reverse transcriptase-polymerase chain reaction (RT-PCR)
OR
Visualization of viruses (NoV) with characteristic morphology by electron microscopy in at least two or more bulk stool or vomitus specimens
OR
Two or more stools positive by commercial enzyme immunoassay (EIA)

*Source: Centers for Disease Control and Prevention. 2011. http://www.cdc.gov/foodsafety/outbreaks/investigating-outbreaks/confirming_diagnosis.html