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 and Laboratory Testing

Laboratory diagnosis depends on the aetiologic agent.

Clinical specimens should be collected from symptomatic cases early in the course of clinical illness to increase the likelihood of detecting a causative agent.

For institutions and public hospitals who implement a food retention policy, 200 grams of potentially hazardous food samples from each meal, frozen at or below -18°C, for 10 days can be submitted to the laboratory for testing if a bacterial pathogen is suspected. If the causative agent of the outbreak is suspected or confirmed to be caused by norovirus, laboratory testing of food retention samples is not recommended.

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 & Outbreak/Case Management

Treatment of individual cases is under the direction of the attending health care provider. Refer to the Recommendations for the Control of Gastroenteritis Outbreaks in Long-Term Care Homes to manage the outbreak.

Whenever there are two cases of infectious gastroenteritis within 48 hours in a specific area such as a unit or floor, an outbreak should be suspected. Early recognition of cases, timely specimen collection, communicating to staff and implementing appropriate control measures can have a positive impact on the course of the outbreak.

An outbreak can be declared at any time by the Medical Officer of Health (or their designate), the Medical Director or the Director of Care for the facility. Laboratory confirmation of an organism is not required to declare an outbreak.

Ongoing monitoring will include: surveillance of residents/patients and staff to identify new cases, monitoring the status of ill residents and staff, monitoring the use of additional precautions/control measures, and implementing control measures for visitors.

Public Health staff will collaborate with the facility and provide guidance and support to the infection control practitioner


Patient Information

Patient Fact Sheet



  1. Ministry of Health and Long Term Care, Infectious Diseases Protocol - Appendix 1 (2022) Gastroenteritis, Outbreaks in institutions and public hospital.
  2. Ministry of Health 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."
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