COVID-19 Laboratory Testing at Public Health Ontario

Laboratory testing is an essential component of Ontario’s response to COVID-19. Not only because it tells us if someone has COVID-19 or not, but also because it sheds light on where and how the virus is spreading.


What’s new?

We have made updates to our COVID-19 whole genome sequencing (WGS) strategy – shifting our focus to building a robust surveillance strategy and public reports

As of October 8, 2021, the provincial COVID-19 WGS strategy includes:

  • 25% of all eligible positive COVID-19 samples (from the variant of concern (VOC) PCR test) are sent for WGS as part of our surveillance strategy. This strategy will continue to detect new and emerging variants, including the Delta variant, in a timely way.
  • This strategy also includes samples from targeted COVID-19 cases such as from international travelers, outbreaks in certain situations, suspected vaccine failure or re-infection cases, or requests from the coroner are also sent for sequencing. This will help detect signs of possible emerging variants and identify issues such as outbreaks, travel-related cases or unusual events.

Laboratory testing is an essential component of Ontario’s response to COVID-19. Not only because it tells us if someone has COVID-19 or not, but also because it sheds light on where and how the virus is spreading.

PHO’s laboratory conducts over 6 million tests every year at our 11 sites across Ontario on a broad range of clinical and environmental samples – operating one of the largest public health laboratory systems in the world.

PHO performs thousands of COVID-19 tests every day in partnership with many hospital, academic and private labs across the province. This network of labs, coordinated by Ontario Health, has come together rapidly since early 2020, in order to meet the increased demand for testing. Find out more about the early days of COVID-19 testing in Ontario.

In addition to performing tests, PHO acts as Ontario’s reference laboratory for COVID-19 testing. This means that we provide support to new labs as they come online with testing and also validate early samples from those labs to confirm the accuracy of the testing. We also validate new test methods (in collaboration with partner labs, including the National Microbiology Lab) and provide expertise to inform the evolution of Ontario’s testing strategy, including how these new methods are implemented.

How is testing for COVID-19 done?

There are two primary methods used in Ontario for COVID-19 testing:

  1. PCR testing (also known as polymerase chain reaction testing), is a type of test that tells us if someone currently has COVID-19. It uses a sample collected with a swab from the person’s nose/throat.

  2. Serology testing tests someone’s blood to see if they have antibodies for COVID-19. This primarily tells us if someone previously had COVID-19. Currently this test is used in limited clinical situations.

Find out more about the difference between these two types of tests and their application.

Whole Genome Sequencing

WGS is a significant tool that helps us understand the evolution and spread of the SARS-CoV-2 virus and can inform outbreak control policies and best-practices.

This laboratory process provides an accurate genetic profile or DNA fingerprint that can detect VOC and Variants of Interest (VOI), and help understand the relatedness between cases.

Who should be tested for COVID-19?

The Ministry of Health develops testing guidance for COVID-19 that is updated as the outbreak continues to evolve and laboratory testing capacity increases.

PHO does not currently recommend routine testing of asymptomatic persons for COVID-19 (outside of those recommended in the guidance from the Ministry of Health, or as directed by the public health unit for public health investigation). However, clinicians should continue to use their discretion to make decisions on which individuals to test.

If you are concerned that you may have been exposed to, or are experiencing symptoms of COVID-19, please visit the Ministry of Health website, take their self-assessment and follow their guidance and instructions. If you are having difficulty breathing or experiencing other severe symptoms, call 911 or go to a hospital emergency room immediately.

Adapting to Future Needs

We work with the Ministry of Health, Ontario Health and other key experts and stakeholders to monitor, provide guidance, and strategize to make sure COVID-19 testing in the province continues to respond to this evolving public health emergency. We explore new test methodologies, like serology, and continue to investigate and validate the use of different types of swabs, reagents, and testing platforms so that our approach can be flexible.


PHO Rounds: Novel Disease Surveillance Tools for the Next Pandemi

This seminar will introduce the concept of informal disease event monitoring systems and how this type of data can and has been used to explore communicable disease epidemiological trends among forcibly displaced persons worldwide. 

See the Event Details
Updated 5 April 2021