Foodborne outbreaks make headlines, but about 95% of foodborne infections are sporadic — single cases not linked to an outbreak — which makes it hard to know what made each person sick. FoodNet, CDC's foodborne disease surveillance network, uses population-based studies to find the foods, exposures and food-handling practices that raise the risk.
How the studies work
Cases come from FoodNet's routine surveillance. Staff interview patients — and, in case-control studies, healthy controls — with a questionnaire, and some studies add molecular subtyping or antimicrobial resistance testing of the bacteria. Questionnaires and protocols are available from foodnet@cdc.gov.
What they found
Campylobacter
| Study | Findings |
|---|---|
| All ages (1998) | risks: chicken or non-poultry meat eaten at restaurants; contact with farm animals, animal stool and puppies. Of the bacteria tested, 11% resisted the antibiotic ciprofloxacin; that resistance was linked to chicken or turkey eaten at commercial establishments and recent foreign travel, and to longer diarrhea |
| Infants under 12 months (2002) | risks: reconstituted formula, well water, living on or visiting a farm, a pet with diarrhea, and riding in a shopping cart next to meat or poultry. Breastfeeding protected |
Salmonella
| Study | Findings |
|---|---|
| Serogroups B and D (1996) | reptile contact raised the risk; breastfeeding protected. Chicken and undercooked eggs were linked to serotypes Enteritidis and Heidelberg; antibiotic use in the previous month to multidrug-resistant Typhimurium DT104 |
| Enteritidis and Newport (2002) | in people who hadn't traveled abroad, Enteritidis was linked to chicken eaten away from home, undercooked eggs at home, and contact with birds and reptiles; Newport resistant to third-generation cephalosporins, to undercooked eggs and beef |
| Infants under 2 months (2002) | risks: reptiles, day care with a child with diarrhea, eating meat, reconstituted formula, and shopping carts next to meat or poultry. Breastfeeding protected |
| Typhi (2002) | strains with reduced susceptibility to fluoroquinolones caused longer fevers and more treatment failures |
| Multidrug-resistant nontyphoidal Salmonella (2006) | a cohort study of how antimicrobial resistance affects patients' outcomes |
E. coli O157 (STEC)
| Study | Findings |
|---|---|
| 1997 | the main risks: visiting a farm, living on or visiting a farm with cattle, pink hamburger at home or away, table-service restaurants, and beef from a private slaughter arrangement |
| 2000 | with PFGE subtyping: pink hamburgers, untreated surface water and cattle farms; fruits and vegetables protected |
| 2006 cohort and genomics studies | a 4-year study of antibiotic exposure and the risk of hemolytic uremic syndrome (HUS), with a linked study of genetic factors — enrollment complete, analysis ongoing |
Other pathogens
| Study | Findings |
|---|---|
| Cryptosporidium (1999) | risks: international travel, contact with cattle, contact with children aged 2 to 11 with diarrhea, and freshwater swimming; eating raw vegetables protected. The study also estimated the illness burden and how much could be traced to food, water, recreational water or farm animals |
| Listeria monocytogenes (2000) | two possible new risks: melons and hummus from commercial establishments |
Long-term care facilities (2005)
A survey of 865 long-term care facilities' food preparation — including their beef, poultry and eggs, and policies on irradiated meat and pasteurized shell eggs — found only three fully following national recommendations to prevent Listeria contamination.
Sources
Based on "Special Studies," FoodNet, Centers for Disease Control and Prevention (page dated September 5, 2024), with the published studies it lists; a work of the United States government in the public domain. The page's photograph, a posed stock-style image, is not reproduced.
Licence: CC0 1.0 (public domain) · Adapted from www.cdc.gov
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