Viral respiratory illness signs and symptoms and severity definitions

Updated November 2, 2023

There is no single sign or symptom of illness that is diagnostic for viral respiratory infections like COVID-19 or influenza. Consider the following symptoms of COVID-19 and other viral respiratory infections:

  • fever
  • headache
  • extreme fatigue
  • loss of appetite
  • body aches
  • cough (new or worse)
  • diarrhea
  • chills
  • sore throat or painful swallowing
  • difficulty breathing
  • nausea and/or vomiting
  • loss of sense of smell **
  • loss of sense of taste **
  • runny Nose **

** These symptoms are more specific to COVID-19

Respiratory illness characterized by predominately serious illness

  • Illness is more than “a bad cold” in many or most of those affected.
  • Illness may be remarkable in its suddenness and accompanying extreme fatigue (prostration).
  • Affected individuals generally are not up and about while ill.
  • Eating and drinking are likely to be affected.
  • Symptoms may persist.
  • There are complications such as pneumonia (viral or secondary bacterial), heart failure or septicaemia in residents or staff for whom pre-existing frailty or underlying chronic illness is not a satisfactory explanation for such complications.
  • Illness may be prolonged, with cases taking longer than expected to recover.

Respiratory illness characterized by predominately mild illness

  • Illness is mild and “common cold-like” in most of those affected.
  • From onset (or within a day or two), activity levels, including eating and drinking, are not markedly different than usual.
  • Note: There may be individual exceptions due to an underlying pre-existing illness that makes certain individuals very susceptible to complications from any respiratory infection.

Viral respiratory illness definitions

Please note: If two or more organisms are identified (e.g. COVID-19 and influenza), consult the medical health officer (MHO) to determine the appropriate follow up

Influenza outbreak

Two or more confirmed client cases within one week on a unit


Enhanced monitoring self management (*)

Site to self manage one or more client COVID-19 cases and transmission on a single unit/floor/neighbourhood by following measures listed in the COVID-19 enhanced monitoring (EM) checklist – one or more case.

  • Public Health will review the submissions of tool 27 daily and see if there are concerning case trends.


Enhances monitoring with Public Health support (*)

In addition to the site following COVID-19 enhanced monitoring (EM) checklist – one or more case.

  • Public Health will contact the site and initiate active Public Health involvement.
  • Additional measures may be recommended at the discretion of the MHO; refer to the checklist for additional measures.

COVID-19 outbreak

This is at the determination of the MHO based on the number of cases identified on a unit, transmission trends, severity of illness and/or operational impacts.

Non-Influenza/non-COVID-19 outbreak (e.g. RSV, other respiratory illness)

Outbreak declaration is at the discretion of the MHO and is based on the situation reported by the care community to Public Health. Consider the following criteria for outbreak declaration when consulting with Public Health:

  • Staff and/or clients on a unit/neighborhood with symptoms of respiratory illness and symptom onset is within seven days.
  • Lab confirmation of the same virus
  • Transmission trends
  • Severity of illness
  • Operational impacts

(*): In general, site management of cases and infection control measures will be at the unit level. There may be situations where more than one unit at a care community is affected. In these situations, there may be a unit in a care community that will be on outbreak while another unit may be on self-management or on enhanced monitoring with Public Health active involvement. Follow up recommendations will be specific to the unit.

  • COVID-19 and influenza staff cases are no longer required to be reported daily to Public Health. Facilities are encouraged to use Tool 28 as a line list to track cases and use the staff checklist available (COVID-19), as needed, for situational assessment and preventative/control measures. Facilities should be able to provide information (e.g., how many staff are sick with respiratory illness and how many are positive for influenza or COVID) if asked by Public Health.
  • If client/resident cases of influenza, COVID-19 or RSV are identified, the care community is to follow the appropriate checklists outlined above and report to Public Health as soon as possible.


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