Version July 2025
| Likely pathogens | Mean incubation period | Classic/common food sources | Other epidemiologic clues |
| Watery diarrhea | |||
| Norovirus | 24 to 48 hours | Shellfish, prepared foods, vegetables, fruit |
|
| Clostridioides (formerly Clostridium) difficile* | N/A | N/A |
|
| Clostridium perfringens | 8 to 16 hours | Meat, poultry, gravy, home-canned goods | |
| Enterotoxigenic Escherichia coli | 1 to 3 days | Fecally contaminated food or water |
|
| Other enteric viruses (rotavirus, enteric adenovirus, astrovirus, sapovirus) | 10 to 72 hours | Fecally contaminated food or water |
|
| Giardia lamblia | 7 to 14 days | Fecally contaminated food or water |
|
| Cryptosporidium parvum | 2 to 28 days | Vegetables, fruit, unpasteurized milk |
|
| Listeria monocytogenes | 1 day (gastroenteritis) | Processed/delicatessen meats, hot dogs, soft cheese, pâtés, and fruit |
|
| Cyclospora cayetanensis | 1 to 11 days | Imported berries, herbs |
|
| Inflammatory diarrhea (fever, mucoid or bloody stools)¶ | |||
| Nontyphoidal Salmonella | 1 to 3 days | Poultry, eggs, and egg products, fresh produce, meat, fish, unpasteurized milk or juice, nut butters, spices |
|
| Campylobacter spp | 1 to 3 days | Poultry, meat, unpasteurized milk |
|
| Shigella spp | 1 to 3 days | Raw vegetables |
|
| Enterohemorrhagic E. coli | 1 to 8 days | Ground beef and other meat, fresh produce, unpasteurized milk and juice |
|
| Yersinia spp | 4 to 6 days | Pork or pork products, untreated water |
|
| Vibrio parahemolyticus | 1 to 3 days | Raw seafood and shellfish |
|
| Entamoeba histolytica | 1 to 3 weeks | Fecally contaminated food or water |
|
* Clostridioides (formerly Clostridium) difficile can also present with inflammatory diarrhea.
¶ Pathogens that are more classically associated with inflammatory diarrhea can also cause watery diarrhea, particularly early in the course of infection.
