From Alpha to Epsilon, all variants of Sars-Cov-2

From Alpha to Epsilon

How dangerous they are, where do they come from, where are they most widespread: a bignami of the known variants of Sars-CoV-2

(Image: Unsplash) Last June 1st, the World Health Organization decided to change the name of the variants of Sars-Cov-2, at least the common one (the scientific one, for example B.1.1.7, will instead be maintained), using the letters of the Greek alphabet instead of a geographical region to avoid incorrectness and discrimination. At the moment, the variants to which the new nomenclature has been attributed are eight (Alfa, Beta, Gamma, Delta, Epsilon, Eta, Kappa, Lambda); others, such as B.1.1.207 first identified in Nigeria in March 2020, or the one found in Denmark in September 2020, are still under investigation and do not yet have a proper name. Let's review them, focusing especially on those that WHO has labeled as variant of concern, that is, which should worry us more than the others.

Alpha

This is the variant B.1.1.7 , identified for the first time in the United Kingdom on 14 December 2020. The one that caused a strengthening of the lockdown on British soil and a further tightening on border controls, so to speak. This variant of the virus has been found more frequently in Southern England, and carries with it as many as 23 mutations, a relatively large number, compared to the original Wuhan strain. Of these, 9 involve the spike protein, and the remaining 14 may have to do with the virus' ability to inhibit the production of interferon by infected cells, which would somehow make the virus invisible to our immune systems.

Alpha spread very quickly in the United States and elsewhere: a study (in preprint) showed that in January the cases of Alpha variant infections doubled more or less every ten days; although the most accredited hypothesis, at the moment, is that the vaccines we have available are also effective against this variant and that its mortality is not greater than the original variant, it is quite certain that its contagiousness is much greater - even up to 70% more, which is why it has been labeled a variant of concern. "Alpha is transmitted much faster than previous variants," explained Neil Ferguson, epidemiologist at Imperial College London, "which means that containment measures may not work well in the future."
< It is not known exactly why this variant is so contagious: several studies seem to suggest that it could be linked to the fact that some of its mutations allow it to enter cells faster. Furthermore, people infected with this variant appear to have a higher viral concentration in the mucous membranes of the ears, nose and throat than those infected with the original variant or other variants.

Beta

That that today we call Beta is the variant B.1.351, identified a few days after the B.1.1.7 in South Africa, and which shares some mutations with the B.1.1.7. Beta soon became dominant nationwide, supplanting the incidence of other variants in the Eastern Cape, Western Cape and KwaZulu-Natal provinces. Like Alfa, it does not seem to be more lethal than others, but it is certainly more contagious, which, again, leads us to evaluate the possibility, in the event of a recurrence of infections, to introduce stronger containment measures than those of the past.

There are also differences: unlike Alpha, the Beta variant seems to be more resistant to vaccines, mainly due to rather significant differences in the structure of the spike protein (the mRna vaccines we have available, in fact, use just the spike protein to teach the body to recognize and fight the virus); at the moment, however, it is still unclear whether it will be necessary to develop another specific vaccine for this variant. Beta has spread quite significantly, in the immediacy of its discovery, to at least five other countries (United Kingdom, Finland, Switzerland, Japan and Australia), and has since reached at least 80 worldwide.

Gamma

The Gamma variant was first identified in Japan on four people returning from a trip to Brazil. It is believed to have developed late last year in the Amazon, soon becoming the dominant variant in the region and surrounding cities; by January 2021 it had already reached several parts of Europe and the United States, and today it is believed to have spread to at least 37 countries.

Several small studies seem to suggest that this variant, a close cousin of Beta, is not particularly ferocious in terms of symptoms and mortality, but, as usual, it is more contagious than the original. It carries the E848K mutation, which involves the spike protein and which therefore, as we have learned, could affect the effectiveness of vaccines, and other mutations which, at least theoretically, could help the virus to evade the antibody response and which could therefore explain its high infectivity.

Delta and Kappa

They are two subtypes of the now famous Indian variant, detected in the Asian nation in October 2020 and rapidly spreading to the United Kingdom, United States and Israel. At the moment B.1.617 (this is its scientific name) is the dominant variant in India, and is the main cause of the monstrous increase in infections in April and May.

The strain that includes the Delta and subtypes. Kappa brings with it two mutations, the E484Q and the L452R: the first is also present in Gamma and Beta, the second in Epsilon. The latter affects the spike protein and could make the virus more infectious, while the former appears to make the virus less susceptible to antibodies developed following a previous infection and possibly also those produced after vaccine administration.

It is not yet known with certainty what can happen when these two mutations are present at the same time on the same virus: the suspicion is that their interaction can make the pathogen even more contagious, a detail that could, at least theoretically, explain the increase in cases in India despite the data indicating that a high proportion of the population was already cured and therefore potentially immune.

The Delta variant also seems to give rise to symptoms such as stomach pain, nausea, loss of appetite more frequently , hearing loss and joint pain, and even the formation of microthrombi so severe that in some cases they lead to gangrene. The scientific community is quite in agreement in considering Delta and Kappa as the most contagious and dangerous variants among those discovered so far.

Eta

Eta, scientific name B.1.525, has also been identified in the United Kingdom: On February 15, a team of researchers from the University of Edinburgh reported seeing it circulating in December 2020. Since then, it has been identified in at least 11 different countries, including Canada, the United States, Ghana, Denmark and Australia, and like the Alpha and Beta variants, it carries the E484 mutation on the spike protein with all the more or less known consequences on the effectiveness of vaccines. "We do not yet know how and how quickly this variant spreads," explained Simon Clarke, associate professor of cellular microbiology at the University of Reading, "but it is presumed that it decreases immunity conferred by the vaccine or by previous infections." >

Epsilon

Epsilon (B.1.427 and B.1.429) is the predominant variant in California, and carries with it the L452R mutation, also present on Delta and Kappa. It was identified in Denmark in March 2020, and has spread quickly to many other countries, including parts of the United States. Twenty-five percent of the samples collected in Northern California between mid-December and early January contained viral material attributable to Epsilon, which equates to a more than six-fold increase in incidence in just under three weeks. >
The variant has given rise to several major outbreaks in Santa Clara County, just outside San Francisco; several recent studies, still in publication, have suggested that Epsilon is more infectious (about 40%) than other variants, and that it seems able to escape more effectively from the immune system's defenses.

Lambda

This is the latest variant discovered, in chronological order. First detected in Peru, it has now spread to over 80 countries and continues to change; it currently constitutes 10% of all new cases of infection detected in the United States (last week it was 6%).

Lambda also appears to be more transmissible and capable of causing more severe symptoms than others , although more studies are needed to confirm these hypotheses. The World Health Organization is observing its epidemiological behavior and its “potential increase in resistance to neutralizing antibodies”.


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