WHY THE MUTATED VARIANTS ARE SO WORRISOME

Viruses mutate all the time, including the novel coronavirus that has caused the global COVID19 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. They don’t appear to be any more virulent, but studies suggest they are more contagious than other strains. More people getting infected could lead to a surge in hospitalizations — as has happened in England and elsewhere — and potentially more deaths. Authorities have imposed new travel curbs and continue to urge people to take precautions in public, such as wearing masks. Drugmakers say their vaccines still should be effective while research is ongoing.

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. It also prompted many places, including the U.S., to halt air and train travel from the U.K. or impose new restrictions. Other countries have followed with tighter lockdowns, particularly in Europe. Health officials warned the strain could become dominant in the U.S. as soon as March. Variants also have been seen in southern Africa and Brazil.

2. What’s causing this?

Preliminary analyses suggest these new variants are more likely to spread among people than other circulating SARSCOV-2 strains. South Africa’s genomic scientists have found the new strain 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. Researchers have found no evidence that it causes a more severe illness.

3. How quickly have they spread?

Rapidly, becoming 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.. 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. In midjanuary, a case was reported in Denmark.

4. Are some mutations more important?

Yes. Scientists pay most attention to mutations in the gene that encodes the SARSCOV-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 recovered and vaccinated patients will be able to fight off the new variants.

5. So will vaccines be effective?

Drugmakers including Pfizer, Biontech, Astrazeneca and Curevac have said they don’t believe their vaccines’ efficacy will be affected, and scientists at the U.S. National Institute of Health are studying the issue.