Covid-19: As ‘Omicron’ fear sets in, a look at the variants that came before it

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As countries see a surge in Omicron cases, the World Health Organisation (WHO) has categorised the variant as a Variant of Concern (VOC) - a mutation of the SARS-CoV-2 associated with increased transmissibility and detrimental change in the way the virus functions and which causes a decrease in the effectiveness of existing public health measures. In addition to VOC, the WHO has previously classified some variants of Covid-19 as Variants of Interest (VOI) and Variants under Monitoring (VUM).

The Brihanmumbai Municipal Corporation (BMC) of Mumbai issued revised Covid-19 guidelines on Friday, making RT-PCR test and home isolation mandatory for people entering the city from countries where the latest coronavirus variant Omicron has been detected. The Maharashtra state government has mandated complete vaccination - that is two shots - for travelling in public transport or visiting public places.

As public health experts and scientists study the severity of the new variant, here's how SARS-CoV-2 has evolved since its detection.

Alpha variant:

The Alpha variant or B.1.1.7 is one of the earliest mutations of the coronavirus. The Alpha variant is designated as a VOC by the WHO. The Alpha variant is 40-80 percent more transmissible than the wild type of SARS-CoV-2. It was first detected in the United Kingdom (UK) in November last year. According to Statista.com, with 2,72,321 cases, the UK has reported the highest number of Alpha variant cases till date. As of November 23, 2021, India has reported over 4,000 cases of Alpha variant.

Read more: Covid-19 virus evolving to get better at becoming airborne: US study

Beta and Gamma variants:

The Beta variant or B.1.351, classified as a VOC by the WHO, was first detected in South Africa in late 2020. The variant was detected in over 20 countries and as of November, the majority of Beta variant cases have been reported from South Africa and France, while India has reported around 245 cases.
Another variant identified as the VOC by the WHO is the Gamma or P.1. The Gamma variant was first detected by Japan among travelers from Brazil. As of November 23, Brazil has reported 44,813 cases of the Beta variant. India has reported five cases of this variant until now.

Delta variant:

According to the Centers for Disease Control and Prevention (CDC), the Delta variant or B.1.617.2 spreads faster than the earlier forms of SARS-CoV-2 and is twice as contagious as the Alpha variant. The WHO has defined the Delta variant as a VOC. It was first identified in India in late 2020 and is currently the predominant variant in the United States and the United Kingdom. By September this year, over 185 countries reported cases of the Delta variant. According to data from Statista, India has reported 45,055 cases of Delta variant so far.

Read more: Explained: All you need to know about new ‘variant of concern' Delta Plus

Delta plus variant:

A sub-lineage of the Delta variant (B.1.617.2), the Delta plus variant or AY.4.2, was first discovered in July this year and became a dominant variant in the UK. In early September, the government of India had said that India has recorded around 300 cases of the Delta plus variant. According to the WHO, the Delta plus variant is considered 15 percent more transmissible than the Delta variant and was reported from 42 countries across the world. While it was tagged as a variant under investigation in the UK, according to the Indian SARS-CoV-2 Genomics Consortium (INSACOG), it is not a variant of concern in India.

Read more: Covid-19 variant: All that is known so far about the new Delta mutation AY.4.2

Kappa and Lambda variants:

The Kappa variant or B.1.617.1 has been classified as a Variant Under Monitoring (VUM) by the WHO. It was detected earliest in India in December 2020. In India, Uttar Pradesh, Rajasthan and Kerala had detected the Kappa variant among the Covid-19 cases reported in the state. At least 44 countries had reported cases of the Lambda variant or C.37 by August this year. The Lambda variant is classified as a Variant of Interest (VOI) by the WHO. Majority cases of the Lambda variant were reported from Chile and Peru.

Read more: Explained: What are the Kappa and Lambda variants of Covid-19? Should you be concerned?

Omicron:

According to WHO, the Omicron variant of coronavirus was first reported from South Africa on November 24. The B.1.1.529 variant is assessed to have a large number of mutations, some of which are concerning. The Omicron variant, according to WHO experts, poses an increased risk of reinfection as compared to other VOCs. South Africa has been witnessing a surge in the Omicron cases in recent weeks. Studies to understand the severity of the variant and the effectiveness of existing vaccines on the new variant are underway. WHO states that there is not enough evidence to suggest that the symptoms associated with the Omicron variant are different from those of other VOCs.

Read more: Amid new variant concerns, BMC revises Covid-19 guidelines