Case Investigation Instructions for FoodNet Counties

FoodNet and Local Public Health Agencies Role

Active, laboratory-based surveillance is the foundation for all Foodborne Diseases Active Surveillance Network (FoodNet) activities. Local Public Health Agencies (LPHAs) conduct case interviews to collect demographic, clinical and epidemiologic information and enter data into the Colorado Electronic Disease Reporting System (CEDRS). These instructions detail procedures that should followed when conducting case investigations in FoodNet counties.
  • FoodNet Case Definition
  • Pathogens
  • Campylobacter
  • Salmonella/Typhoid Fever
  • Shigella
  • Shiga toxin-producing E. coli (STEC)
  • Vibrio
  • Yersinia, non-pestis
  • Cryptosporidium
  • Cyclospora
  • Listeria (CDPHE interview)
  • Laboratory Diagnosis
Detection of one of the pathogens listed above from any specimen site, including stool, urine, blood, CSF and other sites, in a resident of the FoodNet catchment area (Adams, Arapahoe, Boulder, Broomfield, Denver, Douglas, or Jefferson counties). Includes culture-confirmed (detected by culture isolation) and culture-independent (detected only by antigen or PCR methods) cases. FoodNet is actively collecting data on all confirmed, probable and suspect cases as a way to better understand the impact of culture-independent diagnostic tests (CIDTs) on surveillance data. A case does not need to have had symptoms to be considered a case for FoodNet Case Investigation


Complete the relevant CDPHE Case Investigation Form, available on the Communicable Disease (CD) Manual website:

Notes about specific forms:
  • Campylobacter (2 versions): Use the FoodNet version for any cases with isolates available (i.e. reported from Quest Diagnostics). Use the shorter version for all other cases.
  • National case report forms: Cyclospora, Typhoid Fever, and Vibrio. Please upload completed forms for all cases into the CEDRS event. CDC requires submission of national case report forms.


Interviews should be attempted for all FoodNet cases, regardless of specimen source (stool, blood, wound, urine, etc.) or case status (confirmed, probable and suspect). If the case cannot be interviewed, please
contact the patient’s medical provider office to collect as much information as possible. At a minimum, collect information about clinical description, outcome/hospitalization, school/work, contacts and international travel for all cases.

Determining the exposure period can be difficult for cases who do not have an acute onset of gastrointestinal symptoms. It’s important to do a complete assessment for GI illness, even when the specimen was blood, a wound or urine to determine if any GI symptoms were present, even if mild. Use the table below to determine the date for calculating the exposure period:
Guidance for determining exposure period for enteric disease case interviews
If case....
....then use the following date to determine exposure period:
Reports diarrhea or vomiting
Onset date of diarrhea/vomiting.
Does NOT report GI illness, but had onset of other symptoms
Onset date of other symptoms.
Reports NO onset of any symptoms
Specimen collection date.
If a case reports international travel for even one day during the exposure period, it is fine to complete the
travel questions and conclude the interview. No other exposure information needs to be collected.

CEDRS Data Entry

All data collected during case investigation should be entered into CEDRS within five (5) business days of interview completion or contact with provider. Below is a list of required fields.
  • Date of birth (or age)
  • Sex
  • Race
  • Ethnicity

Case Investigation

  • Investigation Status
  • Investigation Start Date
  • Contact Attempts, including date(s), contact method (phone, text, letter) and outcome (Info obtained from provider office, Interview completed)


  • Outbreak, Is this patient part of a known/suspected outbreak?
  • CDPHE Outbreak ID/Name (if known)
  • Outbreak type, select appropriate category (foodborne, waterborne, etc.)

Labs: Please confirm specimen info with case

  • Specimen source (stool, blood, urine, etc)
  • Specimen collection date
  • CDPHE will complete other lab fields (State Lab ID #, tests, results, etc.)

Clinical Description

  • Symptoms: Did patient have symptoms?
    • Diarrhea
    • Bloody diarrhea
    • Fever
  • Onset date (the date of first symptoms associated with this infection)
  • Duration: How many days did illness last?
  • Antibiotics: Did patient take any antibiotics for this illness, During the 30 days before illness, did patient take any antibiotics, and antibiotic names
  • Antacids: During the 30 days before illness, did patient have any form of antacid, and antacid names
  • Probiotic: During the 30 days before illness, did the patient take a probiotic
  • Comorbidities: During the 6 months before illness, was patient diagnosed or treated for cancer, diabetes, or abdominal surgery


  • Outcome (survived/died/unknown): If outpatient, indicate the patient’s status 7 days after specimen collection date. If hospitalized, follow-up until patient discharge or death. If hospitalization is <,7 days,record outcome at time of hospital discharge or death.
  • Hospitalized: Was patient hospitalized? Outpatients who are hospitalized within 7 days of specimen collection, should be recorded as “Yes.” ER visits are NOT hospitalizations. If hospitalized a second time,please enter info for second hospitalization too. If patient hospitalized:
    • Hospital name, Admission date and discharge date
    • During any part of hospitalization, did patient stay in an Intensive Care Unit (ICU) or a Critical Care Unit (CCU)?


  • Employer/School Name
  • Occupation Category
  • Occupation
  • Have a child(ren) in a child care center
  • Attend, work or volunteer at a residential facility
  • Provide direct patient care as a health care worker
  • Work as a food handler

Contact Management

  • Sick contact: Did patient have contact with any individual who had a diarrheal illness (before case’s onset)


  • International travel: Did patient travel outside the US in the 7 days prior to onset? (30 days for Typhoid Fever, 15 days for Cryptosporidium and Cyclospora). If a case reports international travel for even one day​during the exposure period, it is fine to complete the travel questions and conclude the interview. No other exposure information needs to be collected.
  • Domestic travel: Did patient travel within the US in the 7 days prior to the onset of illness?
  • During the 6 months before onset of illness, did patient travel outside the US?
    • If yes, Country(ies) visited
  • During the 6 months before onset of illness, did any member(s) of your household travel outside the US?
    • If yes, Country(ies) visited

Water - Case exposure ascertainment (CEA) questions

  • Well water
  • Septic system
  • Drink untreated water
  • Swim in recreational water and type of water

Pet or animal exposures - Case exposure ascertainment (CEA) questions

  • Visit, work, or live on a farm
  • Visit any animal exhibits
  • Animal contact, including type of animal
  • Contact with sick animal (diarrhea)
  • Animal recently acquired
  • Handle pet food/treats

Restaurant History/ Group Activities

  • Group gatherings
  • Others ill
  • Restaurants, including location details

Grocery/Food Stores

  • Food stores, including location details
  • Food from a farmer's market
  • Food from a CSA, food co-op or home delivery service
  • Food from a specialty store (such as a carniceria, or ethnic market)

Food History - Case exposure ascertainment (CEA) questions

  • Dairy
  • Pasteurized milk
  • Nonpasteurized (raw) milk
  • Soft cheese, including soft cheese made with raw milk
  • Eggs, including eggs eaten out
  • Raw or lightly cooked eggs
  • Chicken, including chicken eaten out, ground chicken, chicken eaten at home bought fresh or frozen
  • Turkey, including turkey eaten out, and ground turkey
  • Rare or undercooked poultry
  • Anyone in household handle raw poultry
  • Beef, including beef eaten out, ground beef, ground beef eaten at home, ground beef prepared elsewhere, pink or raw ground beef
  • Any ground beef in home, even if case did not eat it
  • Anyone in household handle raw beef
  • Fish, including raw or partially cooked fish
  • Seafood, including raw or partially cooked fish
  • Anyone in household handle raw fish or seafood
  • Pork
  • Lamb
  • Veal
  • Liver pate
  • Raw or undercooked liver
  • Sprouts (bean, alfalfa, clover…)
  • Uncooked, fresh tomatoes
  • Lettuce
  • Fresh spinach
  • Uncooked green onions
  • Uncooked cilantro
  • Other fresh herbs (e.g. parsley, basil)
  • Any juice or cider that was NOT pasteurized
  • Cantaloupe
  • Fresh strawberries
  • Any other fresh berries


  • CDPHE Communicable Disease Epidemiology Branch
  • Phone: 303-692-2700 or 800-866-2759
  • Fax: 303-782-0338
  • After hours: 303-370-9395