COVID-19 Variants of Concern
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] ; Associate Editor(s)-in-Chief: Mohamed Riad, M.D.[2] Deekshitha Manney, M. D[3]
Overview
All viruses mutate. Mutations are mistakes that happen in the genetic material of the virus when it replicates. Every single viral replication is an opportunity to mutate. All viruses, including COVID 19 needs a host cell to replicate, because viruses have genetic material but no cytoplasm and cellular proteins to replicate on their own. So the longer a virus replicates and circulates in a population of hosts, the higher chance of a mutation. Not all mutations are significant enough to change the characteristics of virus. However, a sequence of mutations (which is more likely to happen, when the viral load in a community is very high such as in a pandemic), can lead to a change in viral characteristics and can lead to difference either in transmissibility and/or virulence. These mutations can also change the efficiency of vaccines and the viral response to treatment. One of the examples of how viral mutations can affect the efficiency of vaccine is why annual flu vaccines are required. Similar to influenza virus, SARS-CoV-2 (the virus responsible for COVID-19) also can mutate and in a pandemic situation, the likelihood of the mutation and emergence of variants is high. WHO is actively tracking and monitoring the emergence of variants in order to alert the nations and public as part of ongoing response to the current pandemic. Not all variants are of "interest" and/or "concern". The WHO has working definitions for "Variants of Interest (VOI)" and "Variants of Concern (VOC)" as follows:
Variant of Interest or VOI is "A SARS-CoV-2 variant :
- with genetic changes that are predicted or known to affect virus characteristics such as transmissibility, disease severity, immune escape, diagnostic or therapeutic escape; AND
- Identified to cause significant community transmission or multiple COVID-19 clusters, in multiple countries with increasing relative prevalence alongside increasing number of cases over time, or other apparent epidemiological impacts to suggest an emerging risk to global public health."
Variant of Concern or VOC is "A SARS-CoV2 variant that meets the definition of a variant of interest (VOI) and, through a comparative assessment, has been demonstrated to be associated with one or more of the following changes at a degree of global public heath significance:
- Increase in transmissibility or detrimental change in COVID-19 epidemiology; OR
- Increase in virulence or change in clinical disease presentation; OR
- Decrease in effectiveness of public health and social measures or available diagnostics, vaccines, therapeutics."
In the following section, we discuss about all the variants of concern identified by WHO so far, the mutations that were significant, when and where it originated, the impact of the variant on global health.
Variants of Concern
1) Omicron - B.1.1.529 :
The variant was first detected in South Africa. It is designated as VoC, meaning that it can pass between people easily and evade vaccines, treatments, or other protective measures. The number of mutations this variant has is concerning, estimated to be more than 30, which could have a big influence on how this virus behaves.
It is not yet clear whether omicron makes symptoms worse or is severe than other variants like delta. It is also not clear yet how Omicron affects people compared to alpha and delta variants. Infection rates have been increasing from the first week of December-2021 and we need to see how the variant affects the world.
2) Delta - B.1.617.2 :
This variant was first identified in India in early 2020. It is twice as contagious as earlier variants and might cause more severe illness. Most affected people are the unvaccinated people for this variant. Vaccinations do provide protection against this variant.
3) Alpha (B.1.1.7) :