Gastroenteritis, Outbreaks in Institutions and Public Hospitals

Reporting Obligations

Suspected outbreaks must be reported immediately by phone to the Thunder Bay District Health Unit at 625-8318 or toll-free 1-888-294-6630, ext. 8318 (Monday-Friday, 8:30am to 4:30pm). After hours and on weekends/holidays call Thunder Bay Answering Service at (807) 624-1280.

Use the following line list documents:


Aetiologic Agent:

Outbreaks of gastrointestinal illness in institutions are most frequently caused by viruses such as noroviruses, rotaviruses, and rarely other viruses. However, bacteria and other pathogens may cause outbreaks as well.

Clinical Presentation:

The clinical presentation is dependent on aetiology; however, the most common presentation of gastroenteritis is, but is not limited to, abdominal pain, vomiting, diarrhea that is unusual or different for the patient/resident without other recognized aetiology, along with nausea, headache, chills, fever and/or myalgia.

Modes of transmission:

Primarily transmitted through fecal-oral route. May also be transmitted from person-to-person, foodborne, waterborne and droplet contact of vomitus (for norovirus). Transmission may also occur through contact with fomites.

Incubation Period:

Varies depending on the agent.

Period of Communicability:

Varies depending on the agent

Risk Factors/Susceptibility

All persons are susceptible.


Diagnosis & Laboratory Testing

Outbreak Definition: An occurrence of gastroenteritis beyond what is normally expected based on surveillance data. This definition makes it clear why it is important to conduct ongoing surveillance to establish a baseline of normal occurrences for a LTCH. Some additional, simpler outbreak definitions are provided below for guidance. Contact your local Public Health Unit immediately if you suspect an outbreak.

• Suspected Gastroenteritis Outbreak Definition: Two suspected cases of infectious gastroenteritis in a specific area, such as a home, unit, or floor within 48 hours.

• Gastroenteritis Outbreak Definition: Three or more cases with signs and symptoms compatible with infectious gastroenteritis in a specific unit or floor within a four-day period, or three or more units/floors having a case of infectious gastroenteritis within 48 hours.

Note: This definition may be modified as the investigation proceeds.

Laboratory Testing: Submit stool specimens from cases using enteric stool specimen outbreak kits available from the Thunder Bay District Health Unit. Most facilities keep a supply of kits on-site. Test requisition forms are provided with kits.

Testing Information & Requisition


Treatment & Case Management


Patient Information

Patient Fact Sheet



  1. Ministry of Health and Long Term Care, Infectious Diseases Protocol, 2018.  Appendix A (2018) and Appendix B (2018)
  2. Ministry of Helth and Long Term Care. Recommendations for the Control of Gastroenteritis Outbreaks in Long-Term Care Homes, 2018 (or as current).


Additional Resources

  1. Heymann, D.L. Control of Communicable Disease Manual (20th Ed.). Washington, American Public Health Association, 2015.
  2. OHA. "Enteric Diseases Surveillance Protocol for Ontario Hospitals."
Last Updated: 07/05/2019