Coronavirus Variants: Here’s What We Know

As of mid-June, the Delta variant accounted for 99% of Covid-19 cases in the UK, according to Public Health England, and it is expected to represent 90% of cases in Europe by the end of August, according to the European Center disease prevention and control.

The World Health Organization reports that the Delta variant has been detected in 100 countries. It has overtaken the disturbing Beta, or B.1.351 variant, in South Africa.

“The delta is the most transmissible of the variants identified to date,” WHO Director-General Tedros Adhanom Ghebreyesus said last month.

“We know that the Delta variant has increased transmissibility and is currently increasing in pockets of the country with low vaccination rates,” CDC director Dr Rochelle Walensky said Thursday during a briefing at the House. White.

“In parts of the Midwest and high mountain states, early sequence data from the CDC suggests that the Delta variant accounts for about 80% of cases,” she added.

What makes it so much more transmissible? It carries a cluster of mutations on the spike protein – the part of the virus used to attach itself to the cells it attacks – that appear to make it more efficient at getting into cells, where it can replicate.

It also appears to be reaching a point where it can be transmitted two days earlier, on average, after infection, the researchers said in their report published online.

Delta evades the immune system, which can mean that people who have been infected once with an older variant may be more likely to catch it again. It is also immune to the effects of a monoclonal antibody treatment called bamlanivimab, made by Eli Lilly and Co, but is vulnerable to the protection offered by other monoclonal antibody treatments.

The same researchers found that a single dose of the Pfizer / BioNTech or AstraZeneca Covid-19 vaccines was not effective against either the Beta or Delta variants. The antibodies in the blood of only 10% of the people in the study neutralized the Delta variant after a single dose of the vaccine. But a second dose of the vaccine elicited an immune response in 95% of those in the study, although the antibodies were significantly less potent against the Delta variant compared to the Beta variant.

Delta carries a distinct group of mutations compared to other variants, including one called L452R known to increase transmissibility. It does not carry two other disturbing mutations known as E484K and N501Y – which are seen in the B.1.1.7 or Alpha variant first seen in Britain, which swept across many countries in late 2020 and early 2021, and also in the B.1.351 variant of the Beta variant first seen in South Africa, as well as the P.1 or Gamma variant.

Alpha

Last spring, it was the B.1.1.7 or Alpha variant of the coronavirus that worried public health officials. It swept through England quickly and then spread around the world, quickly becoming the dominant lineage in the United States.

As of Sunday, it accounted for only 28.7% of cases in the United States, estimates the CDC, because it was replaced by Delta.

It turned out to be at least 50% more transmissible than older lines. It carries 23 mutations, including one called N501Y which increases transmission.

It is totally sensitive to treatments and vaccines using monoclonal antibodies.

Beta

First seen in South Africa, the B.1.351 or beta variant possesses both the E484K mutation which is linked to immune evasion and the N501Y mutation suspected of helping to make many other variants more contagious. It has been shown to be 50% more transmissible than older strains and escapes double treatment with Lilly’s monoclonal antibody, but not others.

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

Vaccine makers trying to get ahead of newer variants by developing booster shots have focused on B.1.351, as it is the variant that scientists are most worried about escaping vaccine protection. But partial escape does not mean total escape, and vaccines should always protect people to some extent.

It is overtaken by Delta in South Africa and has never really gained a foothold in the United States, where it currently accounts for 0.2% of new cases, according to the CDC.

Gamma

The P.1 or Gamma variant that has swept through Brazil currently accounts for 8.9% of new infections in the United States, according to the CDC.

Gamma carries both the E484K and N501Y mutations, along with over 30 others. It has been shown to escape the effects of treatment with Lilly’s monoclonal antibody, but not that made by Regeneron. Blood tests show that it may partly escape natural immune responses and those caused by vaccination.

Epsilon

The B.1.427 and B.1.429 variants are generally grouped together and known as Epsilon.

First seen in California, this one has the same L452R mutation carried by Delta, but not some of its other mutations and has not taken off like Delta did.

Iota

First seen in New York City last November, the B.1.526 or Iota variant accounts for 3% of cases in the United States, according to CDC estimates. This is down from 9% of samples last April.

It has what’s called a 484 mutation which should help the virus attach more easily to the cells it infects and also make the virus less recognizable to the immune system.

And

First seen in the UK and Nigeria, Eta, also known as B.1.525, carries the E484K mutation. Its frequency is decreasing in the United States, now accounting for almost no samples tested.

Zeta

Circulating in Brazil since last year, this variant, also known as P.2, also carries the disturbing E484K mutation and has not been widely found around the world. He’s almost gone in the United States, according to the CDC.