Comparing COVID-19 variants?
All viruses – including SARS-CoV-2, the virus that causes CoVID-19 – evolve over time. When a virus replicates or makes copies of itself, it sometimes changes a little bit, which is normal for a virus. These changes are called “mutations”. A virus with one or more new mutations is referred to as a “variant” of the original virus. Multiple SARS-CoV-2 variants are circulating globally. Several new variants emerged in the fall of 2020, most notably classified and named based on the recent WHO classification are:
Wuhan or wildtype
The first strain to be identified that originated in the city of Wuhan, China.
Alpha variant
Called B.1.1.7, (the UK variant) was first identified in the fall of 2020. This variant has a mutation in the receptor-binding domain (RBD) of the spike protein at position 501, where the amino acid asparagine (N) has been replaced with tyrosine (Y). The shorthand for this mutation is N501Y. This variant also has several other mutations, including:
· 69/70 deletion: occurred spontaneously many times and likely leads to a conformational change in the spike protein
· P681H: near the S1/S2 furin cleavage site, a site with high variability in coronaviruses. This mutation has also emerged spontaneously multiple times.
It spreads more easily and quickly than other variants, according to the CDC, and potentially is 30% more lethal than the wild-type version, although that is still being investigated. It was first detected in the U.S. at the end of December 2020.
Beta variant
Named B.1.351, it emerged independently of B.1.1.7 (Alpha) and was first detected in South Africa in early October 2020. This variant has multiple mutations in the spike protein, including K417N, E484K, N501Y. Unlike the B.1.1.7 lineage detected in the UK, this variant does not contain the deletion at 69/70.
It shares some of the same mutations as the Alpha strain. Cases in the U.S. were first reported at the end of January 2021. At this time, it is the variant that has most experts the most concerned, because it seems less responsive to existing vaccines and antibody therapies. That said, current evidence suggests it does respond to them, just not as well as the other major known variants.
Gamma variant
The Gamma variant is called P.1 and was first identified in people traveling from Brazil during routine testing in Japan, in early January. The P.1 lineage contains three mutations in the spike protein receptor-binding domain: K417T, E484K, and N501Y. It appears to have a group of additional mutations that affect its ability to be recognized by antibodies, according to the CDC. It was first observed in the U.S. at the end of January 2021.
Lota variant
This variant first appeared in New York City and then sporadically in the northeast. It has been named B.1.526. One of the mutations is similar to that seen in the South African variant that seems to help it evade the body’s response to vaccines. The data on this has, as of February 25, 2021, not been peer-reviewed. The mutation of concern is called E484K, which has been observed in at least 59 different lineages of coronavirus. This means it is evolving independently around the world in what is called convergent evolution.
Epsilon variant
This variant is called B.1.427/B.1.429 and appears different than the alpha (B.1.1.7) variant. One of the mutations, called L452R, affects the virus’s spike protein, which may allow it to attack itself more efficiently to cells, making it more infectious. Again, like the New York variant, the data has not yet been peer-reviewed. However, it appears to be associated with the severity of disease and increased risk of high oxygen requirement. In particular, this virus appears to be prevalent in the San Francisco area.
Delta Variant
The B.1.617 variant, known as the “dual mutant”, has more than two consecutive changes from the older SARS-CoV-2 variant, and little is known about the severity of the disease or the virus’ ability to escape immunity and be vaccinated.
In a genomic and structural analysis of B.1.617 published May 3, 2021, NIV scientists identified eight mutations in the spike virus of SARS CoV-2 virus, two of which are similar to those found in other known types of coronavirus. L452R is known and was first identified in the B.1.427 / B.1.429 variant in California; And three other mutations called E484Q, which are similar to the E484K mutant in the P.1 type, first identified in Brazil in the B.1.315 variant. These mutations make the virus resistant to vaccination.
Scientists are working to learn more about these variants to better understand how easily they might be transmitted and the effectiveness of currently authorized vaccines against them. New information about the virologic, epidemiologic, and clinical characteristics of these variants is rapidly emerging.