Cada coronavírus contém cerca de 30.000 letras de RNA. Essa informação genética permite que o vírus infecte células e as sequestre para fazer novos vírus.

À medida que uma célula infectada cria novos coronavírus, ela ocasionalmente comete pequenos erros de cópia chamados mutações. Os cientistas podem rastrear mutações à medida que são transmitidas através de uma linhagem, que é um ramo da árvore genealógica viral.

Um grupo de coronavírus que compartilham o mesmo conjunto herdado de mutações distintas é chamado de variante. Se mutações suficientes se acumulam em uma linhagem, os vírus podem desenvolver diferenças nítidas em como funcionam. Essas linhagens passaram a ser conhecidas como cepas . Covid-19 é causado por uma cepa de coronavírus conhecida como SARS-CoV-2.

Ao longo da pandemia, surgiram várias variantes do SARS-CoV-2. Alguns deles estão levantando preocupações de que possam prolongar a pandemia ou tornar as vacinas menos eficazes.

Variantes de preocupação

Coronavírus que parecem ser mais infecciosos do que outros coronavírus circulantes.

A linhagem B.1.1.7

Este grupo de coronavírus surgiu na Grã-Bretanha, onde foi denominado Variant of Concern 202012/01 . A variante também é conhecida como 20I / 501Y.V1 ou simplesmente B.1.1.7 .

Acredita-se que os coronavírus da linhagem B.1.1.7 sejam cerca de 50% mais infecciosos . Após sua descoberta em dezembro, emergiu rapidamente em outros países e cresceu a uma taxa exponencial. Está dobrando nos Estados Unidos a cada dez dias . A evidência preliminar sugere que B.1.1.7 é cerca de 35 por cento mais mortal do que outras variantes. Por outro lado, as vacinas parecem funcionar bem contra ele .

B.1.1.7 parece ser mais infeccioso graças a várias mutações em sua proteína spike, que o coronavírus usa para se ligar às células.

MUTAÇÕES PRINCIPAIS EM B.1.1.7

As mutações na proteína spike incluem:

- N501Y , que ajuda o vírus a se agarrar mais firmemente às células humanas. Mas a mutação provavelmente não ajudará o vírus a escapar das vacinas atuais.

- P681H , que pode ajudar as células infectadas a criar novas proteínas de pico com mais eficiência.

- As deleções H69 – V70 e Y144 / 145 , que alteram a forma do pico e podem ajudá-lo a evitar alguns anticorpos.

São necessárias três proteínas de pico para formar um pico, então cada mutação aparece em três lugares:

Para obter mais informações sobre as mutações B.1.1.7, consulte: Por dentro da variante do coronavírus B.1.1.7 .

ONDE B.1.1.7 FOI ENCONTRADO

A variante foi detectada pela primeira vez no Reino Unido em dezembro, e uma olhada em amostras anteriores descobriu-a já em 20 de setembro.

B.1.1.7 has now been detected in over 70 countries. It was first reported in the United States in January, and has now reached at least 33 states.

Last month, the Centers for Disease Control and Prevention warned that B.1.1.7 could become the predominant source of all infections in the United States by March.

RECENT COVERAGE OF B.1.1.7

The B.1.351 Lineage

A variant known as 20H/501Y.V2, from the B.1.351 lineage of coronaviruses, was first identified in South Africa in December.

Scientists are concerned about the variant because clinical trials of vaccines are showing that they offer less protection against B.1.351 than other variants. People who recover from other variants may not be able to fend off B.1.351 because their antibodies won’t grab the viruses tightly. The F.D.A. is preparing a plan for updating vaccines if the variant surges in the United States.

KEY MUTATIONS IN B.1.351

Mutations near the tip of the spike protein include:

— N501Y, which helps the virus latch on more tightly to human cells. This mutation also appears in the B.1.1.7 and P.1 lineages.

— K417N, which also helps the virus bind more tightly to human cells.

— E484K, which may help the virus evade some kinds of antibodies.

WHERE B.1.351 HAS BEEN FOUND

The variant spread from South Africa into neighboring countries, and was detected in the United States in January. It has since spread to at least 24 countries.

It has been detected in three states: Maryland, South Carolina and Virginia.

RECENT COVERAGE OF B.1.351

The P.1 Lineage

A variant known as 20J/501Y.V3 is from the P.1 lineage, an offshoot of the larger B.1.1.28 lineage.

The variant was first reported in Japan, in four people who contracted P.1 on a trip to Brazil. The lineage emerged in late 2020 in Manaus, the largest city in Brazil’s Amazon region. It quickly became the predominant variant there and in several other South American cities.

P.1 is a close relative of the B.1.351 lineage, and it has some of the same mutations on the coronavirus spike protein. It may be able to overcome the immunity developed after infection by other variants.

KEY MUTATIONS IN P.1

Key mutations in the spike protein are similar to those in the B.1.351 lineage, although they arose independently:

— N501Y, which helps the virus latch on more tightly to human cells. This mutation also appears in the B.1.1.7 and B.1.351 lineages.

— K417T, which is the same site as the K417N mutation in the B.1.351 lineage. It may also help the virus latch on tighter.

— E484K, which may help the virus evade some kinds of antibodies.

WHERE P.1 HAS BEEN FOUND

P.1 was discovered in December and reached the United States in January, but it may have been circulating as early as October in Manaus, Brazil. It has now spread to several countries.

P.1 has been detected in two states: Minnesota and Oklahoma.

PREVIOUS COVERAGE OF MANAUS AND P.1

Mutations of Concern

Single mutations that may make the coronavirus more infectious, or help it avoid antibodies.

The D614G Spike Mutation

The D614G mutation emerged in eastern China early in the pandemic and then quickly spread around the world, displacing other coronaviruses that did not have the mutation.

The D614G mutation is thought to make the coronavirus more infections, but it does not appear to make the disease more severe or help the virus escape vaccines.

D614G is so widespread that it has been omitted from other graphics on this page.

PREVIOUS COVERAGE OF D614G

The N501Y Spike Mutation

The N501Y mutation arose independently in several variants of concern, including the B.1.1.7, B.1.351 and P.1 lineages.

The mutation is near the tip of the coronavirus spike, where it seems to change the shape of the protein to be a tighter fit with human cells.

PREVIOUS COVERAGE OF N501Y

The E484K Spike Mutation

The E484K mutation arose independently in multiple lineages, including B.1.351 and P.1. Scientists are also concerned that the mutation was recently found in some samples from the B.1.1.7 lineage from Britain.

The mutation occurs near the top of the coronavirus spike, where it alters the shape of the protein. This change may help the spikes evade some types of coronavirus antibodies.

WHERE E484K HAS BEEN FOUND

E484K has been found in Brazil, Britain, the United States, Canada and Argentina.

RECENT COVERAGE OF E484K

The L452R Spike Mutation

The L452R mutation is not common in the United States, but it has recently spread in California, especially in the Los Angeles area.

The mutation appears in several lineages, and was first observed in Denmark in March. It’s possible that the L452R mutation gives the coronavirus an advantage at spreading over other variants, but the results of experiments that will demonstrate that have yet to come.

WHERE L452R HAS BEEN FOUND

Roughly 45 percent of current samples in California show this mutation.

RECENT COVERAGE OF L452R

Other Variants in the News

These variants have not yet been shown to be more infectious.

The CAL.20C Variant

A variant discovered in California, called CAL.20C, surged in late 2020. The variant spans the B.1.427 and B.1.429 lineages, and carries the L452R mutation listed above. But it’s not yet clear whether it is more infectious.

WHERE CAL.20C HAS BEEN FOUND

By early February, the variant was found in more than half of samples tested in Los Angeles.

PREVIOUS COVERAGE OF CAL.20C

Sources: Bedford Lab, University of Washington; Andrew Rambaut et al. and Nuno R. Faria et al., Virological; Houriiyah Tegally et al., medRxiv; Paul A. Offit et al., Journal of the American Medical Association; Centers for Disease Control and Prevention; GISAID; SARS-CoV-2 lineages. Spike protein model from Ward Lab, Scripps Research. Cahill-Keyes map projection by Gene Keyes.

Tracking the Coronavirus