June 2021: Updates to COVID-19 Variants: Terminology, Laboratory Testing and Reporting
19 June 2021
As new and emerging variants become known, laboratory systems around the world, including our lab at Public Health Ontario (PHO) — which is part of the provincial laboratory network — are required to adapt and shift to proactively monitor for these variants and understand how they are spreading in Ontario.
Starting June 2021, PHO has made updates to part of its laboratory testing strategy for COVID-19 – particularly the provincial whole genome sequencing strategy. Below, we answer your commonly asked questions around how PHO tests for COVID-19 variants of concern (VOC) and what updates we have made to our laboratory testing strategy.
What types of SARS-CoV-2 variants does PHO look for? What is the difference between a VOI and a VOC?
Viruses change and mutate as part of their normal evolution. When there are many mutations in the genetic code of a virus, this is called a variant. As with other viruses, variants are common with SARS-Cov-2 (the virus that causes COVID-19). Although many variants will have no difference in the ability to spread or cause more severe disease, some variants have changes (mutations) which may become concerning.
A variant of concern (VOC) is a variant where its changes have a clinical or public health significance that affects one or more of:
- spread (transmissibility)
- severity of disease (virulence)
- ·vaccine effectiveness
- diagnostic testing
VOC identified globally and in Ontario include:
- Alpha (B.1.1.7 variant first identified the UK)
- Beta (B.1.351 variant first identified in South Africa)
- Gamma (P1 variant first identified in Brazil)
- Delta (B.1.617 variant first identified in India)
A variant of interest (VOI) is a variant that may share one or more mutations in common with a VOC, but do not have enough evidence at this time to be considered a VOC.
PHO’s laboratory testing and surveillance strategy includes identifying and monitoring both VOI and VOC.
To learn more about the new naming conventions for VOC and VOI, check out the World Health Organization’s webpage: Tracking SARS-CoV-2 variants.
How does PHO test for COVID-19 and screen for variants?
PHO’s complete laboratory testing and surveillance strategy includes three key components:
- COVID-19 diagnostic testing (through PCR): the test that tells us if someone currently has COVID-19 by looking for even the smallest amounts of the virus’s genetic material.
- Whole genome sequencing: a laboratory process that looks (called sequencing) into the structure of a virus by reading its entire genetic code. Sequencing the SARS-CoV-2 virus allows us to learn more about the virus, how it’s spreading and how it’s changing (emerging VOC and VOI). It also allows us to detect any early threats posed by VOI and VOC.
- COVID-19 VOC testing (through PCR): Eligible samples that tested positive during the initial COVID-19 diagnostic test are currently sent for VOC PCR testing to determine if a mutation indicating VOC is present in the sample. Our test looked specifically for the N501Y and E484K mutations, which are the mutations associated with three of the predominant VOCs: Alpha, Beta and Gamma. Although this approach is fast, it only looks for variants with these specific mutations and may miss the early introduction of new variants of concern.
What’s new with PHO’s COVID-19 lab testing for variants?
There have been no changes to the COVID-19 diagnostic and VOC test. What’s new is that we have made updates to our COVID-19 whole genome sequencing strategy – shifting our focus to building a robust surveillance strategy and public reports
As of June 14, 2021, the provincial COVID-19 whole genome sequencing strategy includes:
- All eligible positive COVID-19 samples (from the COVID-19 diagnostic test) are sent for whole genome sequencing as part of our surveillance strategy. This strategy will help detect new and emerging variants in a more proactive and timely way.
- This strategy also includes samples from targeted COVID-19 cases such as from the airport, outbreaks, 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.
This new strategy is based on the declining rates of COVID-19 in the province combined with capacity of our whole genome sequencing labs. If COVID-19 cases of COVID-19 increase beyond our whole genome sequencing capacity, PHO will adjust its testing strategy to include taking a random subset of all eligible positive COVID-19 samples to make sure that we have enough information to monitor and detect new variants. Targeted surveillance of the groups listed above will also continue.
Why did we make this change?
Moving to a representative genome sequencing surveillance strategy is aligned with best practices and is also implemented by the European Centre for Disease Prevention and Control and the United Kingdom. This shift allows us to make best use of our resources to monitor and better understand the burden of current VOC in Ontario. It also allows us to identify and track future VOC and VOI in a reliable, timely and proactive way.
Why isn’t the Delta included in the COVID-19 VOC PCR test?
The current approach VOC PCR testing was designed for early detection of the Alpha, Beta and Gamma variants, which at the time of creating the test, were considered rare. This approach was then complemented by whole genome sequencing to confirm the specific variant where needed. This approach has given us a good picture of these three variants.
However, now that VOC are more common, VOC PCR testing is limited in its timeliness of identifying new variants and is particularly important as we monitor for variants that may appear in vaccinated populations. Our new updates to the whole genome sequencing strategy – where all positive COVID-19 samples are sent for whole genome sequencing – allows us to identify and monitor VOC and VOI more proactive and timely way.
Where can I find information and data on COVID-19 variants?
PHO has been working closely with partner labs that perform genome sequencing in Ontario to build and streamline the process of gathering information and reporting on VOCs. We have a series of routine reports and tools where you can find more information, including:
- Ontario COVID-19 Data Tool: Provides information on COVID-19 activity in Ontario to-date, including VOC daily case counts and rates for the Alpha, Beta and Gamma variants.
- COVID-19 in Ontario: Daily and Weekly Epidemiological Summaries: provides daily and weekly data on VOCs, including the number of confirmed COVID-19 cases or VOC detected.
New Epidemiological Summary: SARS-CoV-2 Whole Genome Sequencing: This summary includes data on VOCs (including the Deltavariant) and VOIs from our whole genome sequencing activities conducted by PHO and our partner labs in the Ontario COVID-19 Genomics Network. The data in this report represent the number of samples analyzed and not the number of cases.
If you are responsible for laboratory testing, check out our SARS-CoV-2 (COVID-19 Virus) Variant of Concern Surveillance Test Information Sheet and Labstract for more information.
PHO Rounds: Updates on Influenza, COVID-19, and RSV for the 2023-24 Season
This session will provide an overview of respiratory virus activity in Ontario and Canada during the 2022-23 season and the southern hemisphere’s 2023 season.