In the space of a few months, the Delta mutant strain has reportedly become the predominant worldwide sarS-COV-2 strain. But what came after Delta, how was the new Variant named, and what was the “Variant of Concern”?
For much of the first year of the pandemic, researchers saw SARS-CoV-2 mutate and change as it spread around the globe. It is to be expected that the virus continues to mutate. In fact, viral genomic changes can be so pronounced from person to person that scientists are able to trace the chains of transmission in amazing detail.
Most of the mutations scientists first saw in SARS-CoV-2 were relatively benign. No particular variant seemed to perform better than the others. However, by the end of 2020, a new variant of SARS-CoV-2 was clearly dominant in the UK.
Originally known as B.1.1.7 (also informally known as the British or Kent variant), the rapid spread of this variant clearly indicates that certain mutations produce a distinct transmission advantage. Since then, researchers have been able to identify genomic features unique to the variant and to map out other viral lineages with similar features.
In May, the World Health Organisation (WHO) stepped in to help clear up the growing confusion over the name of the mutant strain. Although scientists often refer to these new variants by their specific genealogical labels (B.1.1.7; B. 1.351; B. 1.617.2; Etc.), but many have found that the origin of the variant (British variant; South African variant; Indian variant, etc.) to mark a variant.
Noting the “stigmatizing and discriminatory” nature of geographical names for varieties, WHO introduced a common naming system based on the Greek alphabet. For research purposes, science departments are still recommended, but national authorities and media organizations are urged to adopt these new, neutral labels.
But if new variants are appearing all the time, when do you get an official tag?
Who’s Technical Advisory Group on Virus Evolution has established three levels of classification for the new SARS-COV-2 variant: Alert requiring further surveillance, “Variant of Concern” (VOI) and “Variant of Concern” (VOC). Now that scientists have a handle on what genomic mutations can significantly alter the severity or transmissibility of SARS-CoV-2, new variants that are likely to be a problem can be found more quickly. These variants were flagged as “alarms requiring further monitoring.”
Who’s current working definition of this designation is: “A VARIANT of SARS-CoV-2, whose genetic changes are suspected to affect the characteristics of the virus, has some indications that it may pose a future risk, but evidence of phenotypic or epidemiological effects is not yet clear and requires enhanced surveillance and reassessment pending new evidence.”
There are currently 13 circulating SARS-COV-2 variants designated as alerts requiring further monitoring.
The next level of classification is “variant of concern” (VOI). These variants have known genetic changes that affect the characteristics of the virus, and they have produced important community clusters in several places. Only when a variant is classified as a VOI is it marked with the characters of the Greek alphabet. There are currently four VOIs designated by WHO.
The final rank is concern mutant (VOC). VOC is a variant that has been shown to have a significant increase in virulence or disease severity. So far, there are four official VOCs, which are defined primarily by their increased transmittability. A variant does not need to spread significantly to be classified as VOC. If evidence is found that a new variant can evade vaccines or current treatments, it will be classified as VOC.
Although there are currently eight official VOIs/VOCs, there are three variants with Greek letter labels that have recently been reclassified as alerts. Epsilon, Zeta, and Theta were all previously classified as VOIs, then downgraded by one name as more epidemiological evidence was collected.
Former VOIs/VOCs will retain their former designation for the time being while they are monitored, who said. Thus Epsilon, Zeta, and Theta currently hold these labels, which means that 11 of the 24 characters in the Greek alphabet are currently used to specify the SARS-COV-2 variant.
Most governments around the world generally accept the WHO label, although some regions do have their own variant grades. For example, in the United States, the Centers for Disease Control and Prevention (CDC) follows a similar designation to WHO and has its own categories of VOI and VOC.
However, the CDC does propose a higher level of classification for variants than VOC, called severe consequences variants (VOHC). It basically covers variants for which there is clear evidence of a significant reduction in vaccine efficacy, or severe clinical disease. Thankfully, no variant of SARS-COV-2 has yet been included in this designated range.
Lambda is a variant of the VOI category recently listed by WHO. In June 2021, it was designated as a “mutant of Concern” (VOC) after significant transmission was detected in Peru over the past few months.