Appendix B: Guidelines for Confirmation of Foodborne-Disease Outbreaks

Appendix B
Guidelines for Confirmation of Foodborne-Disease Outbreaks

A foodborne-disease outbreak (FBDO) is defined as an incident in which two or more persons experience a similar illness resulting from the ingestion of a common food.* The following table provides information about incubation periods, clinical syndromes, and criteria for confirming the etiology once an FBDO has been identified. The information on incubation periods and clinical syndromes is provided as a guideline and should not be included in the confirmation criteria. These guidelines might not include all etiologic agents and diagnostic tests.

FBDOs should be reported to the Foodborne and Diarrheal Diseases Branch at CDC on Form 52.13, Investigation of a Foodborne Outbreak, which was updated in October 1999. Provision of other documents describing the outbreak investigation also is encouraged. For information regarding collection of laboratory specimens and for additional information on viral agents, refer to other CDC publications (i.e., "Recommendations for Collection of Laboratory Specimens Associated with Outbreaks of Gastroenteritis," MMWR 1990:39[No. RR-14] and "Viral Agents of Gastroenteritis: Public Health Importance and Outbreak Management," MMWR 1990;39[No. RR-5]).

* Before 1992, three exceptions existed to this definition; only one case of botulism, marine-toxin intoxication, or chemical intoxication was required to constitute an FBDO if the etiology was confirmed. The definition was changed in 1992 to require two or more cases to constitute an outbreak.

Note:

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Table B. Guidelines for confirmation of foodborne-disease outbreaks

Etiologic agent	Incubation period	Clinical syndrome	Confirmation
Bacterial

1. Bacillus cereus
a. 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
b. 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

2. 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

3. 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

4. Clostridiumbotulinum	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 botulinal toxin in serum, stool, gastric contents, or implicated food
			OR
			Isolation or organism from stool or intestine

5. Clostridium perfringens	6-24 hrs	Diarrhea, abdominal cramps; vomiting and fever uncommon	Isolation of 10⁵ 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

6. Escherichia coli
a. 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
b. 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
c. Enteropathogenic (EPEC)	Variable	Diarrhea, fever, abdominal cramps	Isolation of organism of same enteropathogenic serotype from stool of two or more ill persons
d. Enteroinvasive (EIEC)	Variable	Diarrhea (might be bloody), fever, abdominal cramps	Isolation of same enteroinvasive serotype from stool of two or more ill persons

7. Listeria monocytogenes
a. Invasive disease	2-6 wks	Meningitis, neonatal sepsis, fever	Isolation of organism from normally sterile site
b. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. Vibrio cholerae
a. 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
b. non-O1 and non-O139	1-5 days	Watery diarrhea	Isolation of organism of same serotype from stool of two or more ill persons

14. 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
15. 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

Chemical

1. Marine toxins
a. 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)
b. 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)
c. Paralytic or neurotoxic shellfish	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
d. 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

2. Heavy metals	5 min-8 hrs; usually <1 hr	Vomiting, often metallic taste	Demonstration of high concentration of metal in epidemiologically implicated food
Antimony Cadmium Copper Iron Tin Zinc

3. 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)

4. Mushroom toxins
a. Shorter-acting toxins	2 hrs	Usually vomiting and diarrhea, other symptoms differ with toxin	Clinical syndrome among persons who have eaten mushroom identified as toxic type
Muscimol Muscarine Psilocybin Coprinus artrementaris Ibotenic acid		Confusion, visual disturbance Salivation, diaphoresis Hallucinations Disulfiram-like reaction Confusion, visual disturbance	OR
			Demonstration of toxin in epidemiologically implicated mushroom or food containing mushroom
b. Longer-acting toxins (e.g., Amanitaspp.)	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

Parasitic

1. Cryptosporidium parvum	2-28 days; median: 7 days	Diarrhea, nausea, vomiting; fever	Demonstration of organism or antigen in stool or in small-bowel biopsy of two or more ill persons
			OR
			Demonstration of toxin in epidemiologically implicated food

2. Cyclospora cayetanensus	1-11 days; median: 7 days	Fatigue, protracted diarrhea, often relapsing	Demonstration of organism in stool of two or more ill persons

3. Giardia lamblia	3-25 days; median: 7 days	Diarrhea, gas, cramps, nausea, fatigue	Two or more ill persons and detection of antigen in stool or demonstration of organism in stool, duodenal contents, or small-bowel biopsy specimen

4. Trichinellaspp.	1-2 days for intestinal phase; 2-4 wks for systemic phase	Fever, myalgia, periorbital edema, high eosinophil count	Two or more ill persons and positive serologic test or demonstration of larvae in muscle biopsy
			OR
			Demonstration of larvae in epidemiologically implicated meat

Viral

1. Hepatitis A	15-50 days; median: 28 days	Jaundice, dark urine, fatigue, anorexia, nausea	Detection of immunoglobulin M anti-hepatitis A virus in serum from two or more persons who consumed epidemiologically implicated food

2. Norwalk family of viruses, small round-structured viruses (SRSV)	15-77 hrs; usually 24-48 hrs	Vomiting, cramps, diarrhea, headache	More than fourfold rise in antibody titer to Norwalk virus or Norwalk-like virus in acute and convalescent sera in most serum pairs
			OR
			Visualization of small, round-structured viruses that react with patient’s convalescent sera but not acute sera ?by immune-electron microsopy (assays based on molecular diagnostics [e. g., polymerase-chain reaction, probes, or assays for antigen and antibodies from expressed antigen] are available in reference laboratories)

3. Astrovirus, calicivirus, others	15-77 hrs; usually 24-48 hrs	Vomiting, cramps, diarrhea, headache	Visualization of small, round-structured viruses that react with patient’s convalescent sera but not acute sera ?by immune-electron microsopy (assays based on molecular diagnostics [e. g., polymerase-chain reaction, probes, or assays for antigen and antibodies from expressed antigen] are available in reference laboratories)

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Appendix B Guidelines for Confirmation of Foodborne-Disease Outbreaks

Appendix B
Guidelines for Confirmation of Foodborne-Disease Outbreaks