What We Know About Covid-19 and Its Variants

 

Coronavirus variants and what we know



Omicron is the newest coronavirus variant and is also the quickest to be labeled as a variant of concern by the World Health Organization.

Its emergence has already led to travel restrictions, while high-level government meetings and vaccine makers promise to start working on strain-specific vaccines just in case.

It has a long way to go to take over from Delta, the current variant that dominates all over the world. There’s a long list of variants that at first frightened the world before falling off the map can be a reminder that viruses are unpredictable.

WHO designates coronavirus variants as either variants of concern. The five currently meet the definition for variants of concern: Alpha, Beta, Gamma, Delta and Omicron.


The first sample of the Omicron was taken November 9. It got noticed because of a surge of cases in South Africa.

Some of those mutations were already recognized from other variants and were known to make them more dangerous, including one called E484A.

It also carries a mutation called N501Y, which gives both Alpha and Gamma their increased transmissibility. Like Delta, Omicron also carries a mutation called D614G, which appears to help the virus better attach to the cells it infects.

What worries scientists is the number of mutations affecting the spike protein. That's because most of the leading vaccines target the spike protein. Vaccines made by Pfizer/BioNTech, Moderna, Johnson & Johnson, AstraZeneca and other companies all use just small pieces or genetic sequences of the virus and not whole virus. So a change in the spike protein that made it less recognizable to immune system proteins and cells stimulated by a vaccine would be a problem.

There's no evidence this has happened but there is no way of knowing by looking at the mutations alone. Researchers will have to wait and see if more breakthrough infections are caused by Omicron than by other variants.

Delta

The Delta variant of coronavirus is now the dominant lineage in the US and much of the world. The Delta variant accounts for 99.9% of cases in the US, according to the US Centers for Disease Control and Prevention. It quickly took over from the Alpha variant in most countries.

Delta also carries a cluster of mutations on the spike protein. It can also evade the immune system, which may mean people who have been infected once with an older variant may be more likely to catch it again. 

Alpha

First identified as a variant of concern last December, the Alpha variant of coronavirus was worrying public health officials last spring. It swept across England quickly and then out into the world, quickly becoming the dominant lineage in the United States. It has now been demoted to "Variant Being Monitored" by the CDC because of its low impact in the US.

It was shown to be at least 50% more transmissible than older lineages. It carries 23 mutations, including one called N501Y that increases transmission. It's fully susceptible to monoclonal antibody treatments and vaccines.

Beta

First seen in South Africa, the Beta variant has both an E484K mutation that is linked with immune escape and the N501Y mutation suspected of helping make many other variants more contagious. It has been shown to be 50% more transmissible than older strains.

Blood tests and real-life use both suggest it can infect people who have recovered from coronavirus and also people who have been vaccinated against Covid-19.

It was overtaken by Delta in South Africa and has never gained much of a foothold in the US, despite the worry it caused, and is now designated a Variant Being Monitored by the CDC.

Gamma

The P.1 or Gamma variant that swept Brazil also never gained much ground elsewhere and is also now a CDC Variant Being Monitored.

Gamma carries both E484K and N501Y mutations, with more than 30 others. It has been demonstrated to evade the effects of Lilly's monoclonal antibody treatment but not one made by Regeneron. Blood tests show it might partly escape both natural and vaccine-elicited immune responses.

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