CORONAVIRUS: 7 QUESTIONS ON VARIANTS

Viruses mutate all the time, including the coronavirus that’s caused the global COVID19 pandemic. Although most of the changes are innocuous, several mutants have sparked alarm, and three variants that emerged in the U.K., South Africa and Brazil have caused particular concern.

1. What’s a variant?

During replication, a virus often undergoes genetic mutations that may create what are called variants. Some mutations weaken the virus; others may yield some advantage that enables the variant to proliferate. Variants with distinctly different physical characteristics may be co-termed a strain.

2. How widespread are these variants?

The variant that emerged in England in September, B.1.1.7, contributed to a surge in cases that sent the U.K. back into lockdown in January. Other countries followed, particularly in Europe. In southern Africa, hospitals faced pressure from a resurgence driven by another variant, 501Y.V2 (also known as B.1.351). Brazilian researchers, meanwhile, have warned that a so-called P.1 variant spotted in Manaus in December may have driven a surge in cases that strained the health system and led to oxygen shortages. Researchers in Los Angeles reported a novel strain, denoted as CAL.20C, linked to a surge of coronavirus cases in Southern California, though less is known about its effect on infectivity or disease severity.

3. What are the concerns with these variants?

Broadly, they pose different concerns of varying degrees. These relate to their:

■ Transmissibility, or propensity to spread

■ Severity of illness they cause

■ Neutralization capacity, or the likelihood they will infect people who have recovered from a previous bout of COVID-19

■ Potential impact on vaccination through their ability to evade the protection that immunizations are designed to generate.

4. How are the variants increasing transmission?

They 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. The U.K. strain has acquired 17 mutations compared with its most recent ancestor — a faster rate of change than scientists typically observe. A U.K. advisory group said 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.”

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.

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 will be able to fight off the new variants.

7. Are there any other implications?

Yes, treatments and diagnostics could be affected. Researchers in South Africa found a theoretical risk that some antibodies being developed for therapeutic use could be ineffective against the 501Y.V2 variant prevalent there. But studies at Columbia University support tests by Regeneron Pharmaceuticals showing that its antibody cocktail is effective at neutralizing 501Y.V2 and the variant first identified in the U.K.