Gastroenteritis Outbreak Investigative Guidelines

Investigation Method

1) Collect preliminary data, specifically

• are there > 2 non-householders with gastroenteritis?
• what are the percentages of:
  • vomiting?
  • diarrhea?
  • severe abdominal cramps?
  • fever?
• where did the > 2 non-householders eat?
• when did they eat (date and time)?
• when did they start vomiting or experiencing diarrhea (date and time)?
• what did they eat?
• with whom did they eat?
• did they share other meals in the past week?

2) Call ACDP at 971-673-1111 for referral, if indicated, to the ACDP Urgent Epidemiologic Response Team (UERT).

• Conduct a conference call in accordance with the Outbreak Communication Agreement (pdf) and following the Outbreak Conference Call Agenda (pdf) if the outbreak is in Clackamas, Multnomah, or Washington counties.
• Get patron information and menus from the restaurant using the Foodborne Outbreak Restaurant Checklist (which can and should be used for evaluating other food service establishments).
• Expand the investigation with ACDP/UERT assistance and in accordance with Outbreak Investigation guidelines (pdf).

3) Specimens

• Give outbreak-affected persons Instructions for Collecting Stools for Viral Culture and PCR (pdf)
• Use secure, leak-proof containers with screw tops, not flip tops, labeled with name, collection date, and outbreak number.
• Collect specimens of walnut-size stool, 3 tbsp of diarrheal stool (or vomitus) or 3-4 rectal swabs from five outbreak-affected persons up to four days after onset. Collecting >5 does not increase the chance of finding something.
• Remember that two positives are required to "confirm" the microbial cause of an outbreak. The Oregon State Public Health Laboratory will not test just a single specimen.
• Based on epi curve and symptom profile, determine whether the etiology is likely to be viral or bacterial.* Complete instructions for specimen submission are available on the OSPHL Lab Test Menu at www.healthoregon.org/labtests.
• If likely to be viral, follow the instructions above for collecting stool specimens for viral culture and PCR. Choose the OSPHL Lab Test Menu listing for "Viral Gastroenteritis Panel, PT-PCR".
  
• If likely to be bacterial, collect stool specimen in a Cary Blair transport media. Choose the OSPHL Lab Test Menu listing for “Enteric Pathogen Culture, Bacterial".
  
• If additional testing is thought to be warranted, consult with ACDP regarding possible bacterial culture or multiplex PCR testing at OSPHL.

4) Complete record in Outbreak database

• Submit no later than 30 days after the onset of the last case
  

Special Situations

Definition, suspect foodborne outbreak

• > 2 non-householders who develop gastroenteritis (acute onset vomiting, diarrhea or both) at about the same time after eating food from the same source

Investigative authority

• ORS 333-018-0015 authorizes local health departments to investigate foodborne and other common source outbreaks by requiring health care providers to report all such suspected outbreaks immediately.  
• ORS 333-019-0010 imposes work restrictions on persons who work at food service facilities whilst in a communicable stage of any illness accompanied by diarrhea or vomiting.
• ORS 624-080 authorizes local health departments to collect stool specimens from food handlers.