ARI Outbreaks in All Congregate Living Settings and Child Care

The Ontario Ministry of Health and Long-Term Care have set case definition criteria for outbreaks:

ARI Outbreaks in LTCH, RH and Other Congregate Living Settings


Suspect Respiratory Outbreak:

  • Two or more client cases of acute respiratory infections (ARI) with symptom onset within 48 hours and an epidemiological link (e.g., same unit/floor/service area) suggestive of transmission within the setting AND testing is not available or all negative. 

Confirmed Respiratory Outbreak:

  • Two or more client cases of test-confirmed acute respiratory infections (ARI) with symptom onset within 48 hours and an epidemiological link (e.g. same unit/floor/service area) suggestive of transmission within the setting.

    OR

  • Three or more client cases of ARI with symptom onset within 48 hours and an epidemiological link suggestive of transmission within the setting AND testing is not available or all negative.

Client Case Definition:

  • Two or more new and unexplained respiratory symptoms not attributed to an underlying medical condition (e.g., COPD, allergies, etc.) for the individual.

Clinically Compatible Signs & Symptoms:

  • Fever/abnormal temperature
  • Dry cough
  • Productive cough
  • Headache
  • Nasal congestion
  • Congestion/sneezing
  • Sore Throat/hoarseness
  • Muscle aches
  • Malaise/fatigue

For more information, refer to Ministry of Health and Long-Term Care document:


Resources and Guidance




List of links present in page
  1. https://www.wechu.org/infectious-diseases/other-acute-respiratory-infections-ari
  2. https://www.ontario.ca/files/2025-02/moh-recommendations-for-outbreak-prevention-and-control-in-institutions-and-cls-en-2025-02-28.pdf
  3. https://www.ontario.ca/files/2025-09/moh-ophs-respiratory-infection-outbreaks-en-2025-09-17.pdf
  4. https://www.ontario.ca/files/2024-11/moh-ophs-coronavirus-disease-2019-en-2024-11-01.pdf
  5. https://www.ontario.ca/files/2025-04/moh-ophs-influenza-en-2025-04-01.pdf
  6. https://www.wechu.org/infectious-diseases/covid-19
  7. https://www.wechu.org/infectious-diseases/influenza
  8. https://www.wechu.org/tags/infectious-disease-prevention