What are Variants?
When viruses infect cells and replicate their genetic material, errors occur. While many of these errors, or genetic mutations, have little effect, some can be harmful to the virus. Others can cause small changes in viral proteins and give viruses new abilities. These abilities can include making the virus more infectious, more resistant to vaccines and therapies, and sometimes making our antibodies or immune systems less effective against these modified viruses. Viruses containing genetic mutations are called variants, and those with a suspected or confirmed advantage are called variants of interest and variants of concern, respectively.
Variants continue to emerge as long as the virus is able to spread to new hosts. Vaccines train our immune system to recognize different parts of the virus before we get infected. Therefore, if mutations change the parts used for this training, vaccines become less effective and need to be updated. This is why variants must be tracked and analyzed continuously.
What are Variants?
When viruses infect cells and replicate their genetic material, errors occur during this process. While many of these errors, or genetic mutations, have little effect, some can be harmful to the virus. Others can cause small changes in viral proteins and give viruses new abilities. These abilities can include making the virus more infectious, more resistant to vaccines and therapies, and sometimes making our antibodies or immune systems less effective against these modified viruses. Viruses containing genetic mutations are called variants, and those with a suspected or confirmed advantage are called variants of interest and variants of concern, respectively.
Variants continue to emerge as long as the virus is able to spread to new hosts. Vaccines train our immune system to recognize different parts of the virus before we get infected. Therefore, if mutations change the parts used for this training, vaccines become less effective and need to be updated. This is why variants must be tracked and analyzed continuously.
Variants of Concern vs. Variants of Interest
Variants of concern (VOCs) are mutations of SARS-CoV-2 that are confirmed to be more infectious, can potentially cause more severe disease, and may be more resistant to existing vaccines compared to the original strain. CoVaRR-Net is working alongside other organizations in Canada and around the world to investigate VOCs and emerging new variants.
There is currently only one circulating VOC in Canada: Omicron, which has become the dominant variant in Canada and around the world. Its parent lineage, B.1.1.529, was first reported to the WHO from South Africa in late November 2021. Omicron now includes BA.1, BA.2, BA.3, BA.4, BA.5 and descendent lineages. It also includes circulating recombinant forms such as BQ and XBB. XBB.1.5 is one of the currently fastest growing lineages worldwide (January 2023).
A variant of interest (VOI) is one that is only “suspected” to either be more contagious than the initial strain, cause more severe disease, or escape the protection offered by vaccines. A VOI can become a VOC if more scientific and clinical evidence emerges that it acquires one or more of these attributes.
There is no currently circulating variant of interest (VOI) in Canada. Previously circulating VOIs include Eta (B.1.525), Kappa (B.1.617.1), Iota (B.1.526), Epsilon (B.1.427/B.1.429), Zeta (P.2), Theta (P.3), Lambda (C.37) and Mu (B.1.621).
A variant under monitoring (VUM), according to the World Health Organization (WHO), is a SARS-CoV-2 variant with genetic changes that are suspected to pose a future risk. It is important to carefully monitor and repeatedly assess VUMs until evidence of their impact is clear.
Simplified SARS-CoV-2 evolutionary tree
WHO:
The World Health Organization started May 31, 2021 to give Greek letters (e.g., Alpha, Beta, Gamma, and Delta) according to the order of the detection of variants.
PANGO:
Phylogenetic Assignment of Named Global Outbreak, a nomenclature system defining the dynamic nomenclature of SARS-CoV-2 lineages.
Clade:
A group of genetically similar viruses derived from a common ancestor.