Clinical Considerations

Clinical Considerations

Vulnerable populations

Most people who get COVID-19 will experience mild to moderate symptoms. However, some groups are at higher risk for more serious illness, complications and death. These groups include:1

  • Older adults (>60 years old)
  • Those with chronic or pre-existing conditions (i.e., heart disease, diabetes, chronic respiratory disease, cancer)
  • Individuals with compromised immune systems

Socio-economic factors can also contribute to increasing vulnerability of individuals to COVID-19, increasing their risk of negative health outcomes. This includes people who use substances, are unsheltered, employed in precarious work, or live in isolated communities, such people may face additional challenges in applying preventive strategies or gaining access to necessary resources.2,3 The Public Health Agency of Canada (PHAC) provides guidance on how organizations and health-care providers can support vulnerable populations.


Note: the following section considers signs or symptoms experienced by people infected with COVID-19 during the Omicron wave.

There is some evidence to indicate that a large proportion (~30%) of people infected with COVID-19 may have little or no symptoms at all. For those who do develop symptoms, they may take up to 10 days to appear, though the average is 2-4 days from exposure to symptom onset. Those who have received a full series of a COVID-19 vaccination typically experience less-severe symptoms.1 The virus can be transmitted by individuals infected with COVID-19 with or without symptoms.1

Frequency of symptoms reported by people infected with COVID-19

Common symptoms (>50%)

  • Runny nose
  • Sneezing
  • Sore throat
  • Headache

Less frequent symptoms (<50%)

  • Persistent cough
  • Joint pain
  • Chills
  • Fever
  • Dizziness
  • Muscle pain
  • Gastrointestinal symptoms (nausea, diarrhea, abdominal pain)
  • Hoarse voice
  • Loss of or altered sense of smell

Rare symptoms (<10%)

  • Swollen glands
  • Chest pain
  • Irregular heartbeat
  • Shortness of breath
  • Skin changes
  • Delirium
  • Confusion/brain fog


People infected with COVID-19 during the Omicron wave are less likely to experience symptoms such as cough, fever, chills, and muscle pain, which were common symptoms during the Delta wave. It is important to note that symptom patterns will change as new COVID-19 variants emerge.

Detection and reporting

Diagnosis of COVID-19 is made through a combination of examining clinical presentation, epidemiology, and lab confirmation. Lab confirmations of COVID-19 include:

  1. Nucleic acid-based testing (NABT)4
    NABT is most often referred to as molecular testing, which detects the virus’s genetic material (nucleic acids) and is the gold standard for COVID-19 diagnosis. Polymerase chain reaction (PCR) is the most common type of molecular testing.
  2. Rapid antigen detection test (RADT)5
    The RADT is most often referred to as COVID-19 rapid tests. Rapid tests detect virus proteins and provide results in less than one hour. Rapid tests are less sensitive than molecular testing. For health professionals, familiarize yourselves with the interim guidance on antigen testing:
    • Positive results should be deemed as “presumptive” cases until confirmed by a PCR test.
    • When interpreting negative results, the clinical context of the test (symptomatic versus asymptomatic) and the pre-test probability of COVID-19 infection in the person tested should be considered.

If pre-test probability of infection is high (e.g., known exposure to person with COVID-19, high community transmission), further testing using a PCR test should be conducted.

Important information for health professionals on diagnosis and reporting from the Public Health Agency of Canada:

As testing may vary by province, we encourage you to seek specific information from the jurisdiction in which you reside or practise.

Knowledge/resource/practice gaps

Throughout the pandemic, each province and territory has adapted their testing guidance (molecular and rapid testing) based on several factors, including growing evidence, new technology or devices, laboratory capacity, and epidemiological contexts.6

Further, COVID-19 variants have had significant implications on case and contact management for provinces and territories due to higher transmissibility, potential for immune invasion, and disease severity.6 These implications mean that testing is more conservative since the onset of the pandemic , and as such, the true number of cases and true rate of community transmission is not known.

COVID-19 variants

In general, viruses are constantly changing. Viruses are classified as variants when there have been significant mutations. Variants are of concern when there is an impact to disease spread, disease severity, testing or detection, and vaccine or treatment effectiveness.7

As of December 2021, several COVID-19 variants of concern have been identified in Canada:

  • Alpha (B.1.1.7)
  • Beta (B.1.351)
  • Gamma (P.1)
  • Delta (B.1.617)
  • Omicron (B.1.1.529)

Considering the Omicron variant, the Public Health Agency of Canada (PHAC) provides the following recommendations for health-care settings:

  • Continue to maintain, evaluate, and monitor existing COVID-19 infection prevention and control measures
  • Continue to implement and re-evaluate the hierarchy of controls
  • When in close contact or within two metres of a person with suspected or confirmed COVID-19, wear a well-fitted respirator, eye protection (e.g., goggles or face shield), gowns, and gloves
  • Personal protective equipment for all patient encounters should be based on a point of care risk assessment

Evidence is continuing to evolve on the quantification of aerosol production by aerosol generating medical procedures (AGMP). PHAC continues to recommend the use of fit-tested N95 respirators, eye protection, gowns, and gloves during AGMPs.

Case and contact management

Management of cases and contacts may vary by province or territory based on epidemiology, vaccination rates, variants of concern, vaccination status of contacts, and other considerations. PHAC’s recommendations on case and contact management focuses on the following:

Contact management

  • As per PHAC, the purpose of contact management is as follows:
    • To identify contacts and support containment, reducing transmission to others in the community
    • To promote early implementation of public health measures for contacts
    • To gain more information/understanding about SARS CoV 2
  • Depending on exposure level risk assessment, contacts are placed into either high or low risk categories, and managed according to the corresponding recommendations for that risk level.

Case management

  • Reporting and notification
  • Lab testing
  • Clinical management/treatment
  • Case management in home and co-living situations
  • Public health monitoring of cases and persons under investigation