Viruses mutate all the time, including the novel coronavirus that’s caused the global Covid-19 pandemic. Most of the changes have no apparent effect. But recent variants that have emerged in the U.K., South Africa and Brazil are causing particular concern. Studies suggest they are more contagious, and some evidence points to the U.K. strain being more deadly. An increase in infections has led to a surge in hospitalizations and deaths in England and elsewhere. Drugmakers say their vaccines should still work, but some researchers warn the shots may need to be updated periodically to maintain their efficacy.

1. How serious is this?

The variant that emerged in southeast England in September, dubbed the B.1.1.7 lineage, contributed to a spike in cases in December that sent the U.K. back into lockdown. Other countries have followed, particularly in Europe, and are ratcheting up precautions like wearing masks. The European Centre for Disease Prevention and Control on Jan. 21 raised the risk of spread of the new variants in the European Union to “very high.” In the U.S., health officials have warned the strain could become dominant there as soon as March; President Joe Biden toughened rules in his first days in office to try to contain it. In southern Africa, hospitals are facing pressure from a resurgence driven by another variant, 501Y.V2. Brazilian researchers are warning that a so-called P.1 variant spotted in Manaus, Amazonas state, in December may have driven a surge in cases that strained the health system and led to oxygen shortages. The variant has been found in Japan and South Korea among travelers from Brazil. Researchers at Cedars-Sinai Medical Center in Los Angeles say a novel strain has emerged in California, though less is known about its importance.​

2. What’s causing this?

Preliminary analyses suggest these new variants are more likely to spread faster among people than other circulating SARS-CoV-2 strains. South Africa’s genomic scientists have found the new strain there can infect human cells more efficiently and is about 50% more transmissible than earlier versions. The variant in the U.K. has been found to be 56% to 70% more transmissible. It has acquired 17 mutations compared to its most recent ancestor -- a faster rate of change than scientists typically observe. Prime Minister Boris Johnson said Jan. 22 that new evidence had led the government to revise its original view that the variant was not more dangerous. The government said that on average, for 1000 men in their 60s, 13 to 14 would die if they contracted the new variant, compared to 10 for the original strain.

3. How quickly have the strains spread?

Rapidly. They have become the dominant strains in multiple countries, aided by year-end holidays that are traditionally associated with increased family and social mixing. By early January, cases caused by the B.1.1.7 variant had been identified in some 50 countries or territories, including the U.S., Australia, Canada, Germany, Italy, Japan, Lebanon, the Netherlands, Singapore and South Korea. Similarly, the 501Y.V2 variant that was first detected in Nelson Mandela Bay, South Africa, in early October has led to a steep rise in cases across nine southern African countries as well as the Seychelles and Mauritius. By mid-January, 501Y.V2 had been identified in 10 countries in Europe, with clusters of cases reported in the U.K. and Israel and another under investigation in France.

4. How much are the variants increasing transmission?

The new variants appear to have some advantage over other versions that has enabled them to quickly predominate, although factors such as people congregating indoors more in colder weather may also contribute to spread. A U.K. advisory group noted in December that the B.1.1.7 lineage may result in an increase in the basic reproduction number, or R0 (the average number of new infections estimated to stem from a single case) in the range of 0.39 to 0.93 -- a “substantial increase in transmissibility compared to other variants.” Infection rates in areas where the strain has been circulating have increased faster than expected, Public Health England said. It reported in January that patients infected with the variant were more likely to infect their contacts than if they had a “regular” strain.

5. How many mutations are there?

Many thousands of mutations and distinct lineages have arisen in the SARS-CoV-2 genome since the virus emerged in late 2019. A variant with a so-called D614G mutation emerged in early 2020. By June, it had replaced the initial strain identified in China to become the dominant form of the virus circulating globally. Months later, a novel variant linked to farmed mink was identified in a dozen patients in North Jutland, Denmark, but doesn’t appear to have spread widely. As mutations continue to arise, they will lead to more new variants.

6. Are some mutations more important?

Yes. Scientists pay most attention to mutations in the gene that encodes the SARS-CoV-2 spike protein, which plays a key role in viral entry into cells. Targeted by vaccines, this protein influences immunity and vaccine efficacy. The B.1.1.7, 501Y.V2, and P.1 variants all carry multiple mutations affecting the spike protein. That raises questions about whether people who have developed antibodies to the “regular” strain -- either from a vaccine or from having recovered from Covid-19 -- will be able fight off the new variants. In January Public Health England found those previously infected with the “regular” coronavirus are likely to mount an effective antibody response against the B.1.1.7 variant. But that same month the first known instance of a recovered Covid-19 patient being reinfected with the P.1 variant was reported in Brazil.

7. So will vaccines be effective?

Research is ongoing, but results so far are inconclusive. Research in South Africa and at Rockefeller University in New York found reason for concern:

• South Africa’s National Institute for Communicable Diseases studied blood samples from 44 patients previously infected with the coronavirus to check if their antibodies would fight off the new variant there. The cohort was small but, worryingly, half of the samples tested indicated all neutralizing activity was lost, suggesting that those people may no longer be protected. In the others, antibody levels were reduced, but those individuals had started from a higher level, having recovered from severe Covid-19. The scientists cautioned that the lab studies are only indicative. They said they have no evidence that this is actually occurring in the community, or whether vaccine-generated antibodies will be less effective against the new strain.

• Experiments at Rockefeller University indicate that variants, including B.1.1.7, 501Y.V2 and P.1, may negate the potency of the Moderna Inc. and Pfizer-BioNTech vaccines, according to a study released on Jan. 19 ahead of publication and peer-review. Researchers are working to understand this better.

8. What are drugmakers doing?

Pfizer Inc.’s German partner, BioNTech SE, said the results of a lab study released in mid-January indicated that it’s “very unlikely that the U.K. variant viruses will escape” protection from their so-called mRNA vaccine, echoing statements from rival vaccine makers. Still, BioNTech said it’s ready to adapt the vaccine if needed. The University of Oxford, which partnered on the AstraZeneca Plc vaccine, said it’s evaluating what it would take for rapid deployment of “adjusted” versions to combat emerging variants if needed. Such alterations aren’t unheard of -- it happens annually with seasonal flu, which evolves quickly. Unlike flu, coronaviruses have a genetic self-correcting mechanism that minimizes mutations.

9. Are there any other implications?

Yes, treatments and diagnostics could be affected. Researchers in South Africa have found that some antibody therapies, including the Regeneron Pharmaceuticals Inc. product granted emergency use authorization in the U.S. and administered to Donald Trump, may be ineffective against the 501Y.V2 variant. The U.S. Centers for Disease Control and Prevention has said new strains might undermine the performance of some PCR-based diagnostic tests. The impact, though, isn’t likely to be significant, according to the World Health Organization.

(Updates with U.K. warning that its strain may be more deadly.)

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