Viruses keep mutating and changing its genetic constitution constantly. This leads to formation of new variants of the virus over time. Interestingly, these new variants can either disappear or persist in the long run.
Even during the current COVID-19 pandemic, numerous variants of the SARS-CoV-2 (the coronavirus that causes COVID-19) have been documented globally. Each coronavirus contains a sequence of approximately 30,000 nucleotides of RNA which are like sequence of repeating alphabets. When the virus infects a living cell, it makes copies of itself. While making copies, there might occur certain minor copying errors known as mutations resulting in a new strain of the virus as the mutation passes to a new host.
Classification of Variants
The Centers for Disease Control and Prevention (CDC) has classified the SARS-CoV-2 variants into three types –
- Variants of Interest (VoI)
- Variants of Concern (VoC)
- Variants of High Consequence (VoHC)
Variants of Interest (VoI)
These are variants with specific genetic markers that have been associated with
- changes to receptor binding
- reduced neutralization by antibodies generated against previous infection or vaccination
- reduced efficacy of treatments
- potential diagnostic impact
- predicted increase in transmissibility or disease severity
CDC has classified four SARS-CoV-2 variants as VOI. The mutations may help the virus to dodge antibodies and treatment but is not as infectious as VOC.
Variants of Concern (VOC)
These are variants for which there is evidence of
- an increase in transmissibility
- more severe disease (e.g., increased hospitalizations or deaths)
- significant reduction in neutralization by antibodies generated during previous infection or vaccination
- reduced effectiveness of treatments or vaccines
- diagnostic detection failures
Currently, there are five SARS-CoV-2 VOCs according to CDC. All the five variants share one specific mutation called D614G which makes the virus more transmissible than its original form.
Variants of High Consequence (VoHC)
These variants show clear evidence that prevention measures or medical countermeasures have significantly reduced effectiveness relative to previously circulating variants. Currently there are no SARS-CoV-2 variants of high consequence.
The Indian Variant of SARS-CoV-2
The B.1.617 variant also known as VUI (Variant Under Investigation)-21APR-01 was first detected in India in October 2020 and then in other countries around the world. The Indian variant consists of two mutations (E484Q and L452R) on the surface spike protein of the virus and hence is called a “double mutation” variant. Recently, a third mutation (V382L) was found during the second wave of the pandemic thus terming it as a “triple-mutant COVID.”
However, since there are many double and triple mutants all over the place, the terms double and triple mutant COVID are typically a misnomer. Also, the variant has many more defining mutations apart from these three; hence the name can be misleading as well.
Of Interest or Of Concern?
The World Health Organization (WHO) has warned against jumping to conclusions about the Indian variant. The CDC has also not categorized the Indian variant yet. Although many have pointed out at the variant as the culprit in the soaring number of infections in the second wave, experts have put the onus of the upsurge on large gatherings, festivals, rallies and lack of preventive measures such as mask-wearing or social distancing. Scientists do not yet know whether this variant is more infectious or resistant to vaccines.