Scientists around the world are scrambling to learn more about previously unknown variants of the coronavirus that seem to spread from person to person more readily than other versions of the Covid-19-causing pathogen—including one variant that may also be more deadly.
A fast-spreading variant, known as B.1.1.7, was identified in December in the U.K., leading to travel restrictions and a widespread lockdown there. Since then, the U.K. variant has been detected in China and other countries, as well as in Colorado, California and Florida.
Now there’s preliminary evidence suggesting that the variant could lead to more deaths.
“We have been informed that, in addition to spreading more quickly, it also now appears that there is some evidence that the new variant—the variant that was first identified in London and the South East—may be associated with a higher degree of mortality," British Prime Minister Boris Johnson said.
In South Africa, meanwhile, doctors and researchers battling a second surge of Covid-19 cases are studying another new variant and what role it plays in the rising tide of cases there. The variant, known as B.1.351, has been identified in samples dating back to October. It hasn’t been detected in the U.S. Emerging data suggests that this variant could be better at evading antibodies, the protective immune-system proteins that keep viruses from entering cells, and that existing vaccines may need to be updated in order to be effective.
Here is what we know so far about the new variants and the genetic mutations that characterize them, as well as their potential impact on public health.
What is a viral variant?
Viral variants are new versions of a virus that arise as a result of small changes in its genetic code. Over the course of the pandemic, there have been several variants. Those that proved able to spread more efficiently have become more prevalent, while others fizzle out. “It’s just like natural selection, like evolution," said Bettie Steinberg, a virologist and provost at Northwell Health’s Feinstein Institutes for Medical Research.
Why the concern about these particular variants?
Preliminary data from U.K researchers suggests that infection with the U.K. variant could cause more severe disease and potentially lead to more deaths. The data showed that patients infected with the variant had a higher risk of death than those infected with previous versions of the virus.
Britain’s top scientific adviser said preliminary studies show that the U.K. variant might be 30% to 40% deadlier than previous variants.
U.K scientists cautioned that a fuller understanding of the variant’s effects on health would emerge in coming weeks as more data on hospitalizations and mortality becomes available.
Some doctors were already worried that the new variants of the coronavirus could supercharge the spread of Covid-19, putting additional stress on hospitals and nursing homes when cases are near their historic highs.
Researchers from the London School of Hygiene and Tropical Medicine combined behavioral and epidemiological data on patterns of disease transmission with mathematical models to determine whether the U.K. variant is more transmissible than previously identified variants.
They found the new variant to be more transmissible than previous variants.
U.K. contact-tracing data show that patients infected with the new variant went on to infect more people than those infected with previous variants. Data also suggested that the viral load, or the amount of virus in the body, was higher among people infected with the new variant. The higher the viral load for individuals, the more infectious they tend to be.
Could poor adherence to social distancing and similar measures be driving the spread of new variants?
Scientists don’t think so, at least for the jump in cases in the U.K. As evidence, Prof. Neil Ferguson, an epidemiologist at Imperial College London and a member of a scientific panel that advises the British government on respiratory-virus threats, pointed to epidemiological data from November showing that cases of the new U.K. variant were exploding in the area southeast of London as coronavirus cases were falling in other parts of the country. The entire country was in lockdown during this period.
The situation may be different in South Africa, where researchers said human behavior might be playing a key role in the surge of cases. Millions of South Africans traveled widely in recent weeks, and tens of thousands had gathered in restaurants and bars and on beaches during the holiday season.
What gave rise to the new variants?
Like other viral pathogens, the coronavirus spreads by infecting cells and then reproducing within them, creating copies of itself that spread throughout the body and then are shed, potentially infecting other people.
The reproduction process involves copying the virus’s genetic code, which holds the instructions for building successive generations of virus particles, or virions. But the code isn’t always reproduced faithfully; sometimes the copying process yields mistakes that researchers have likened to typographical errors. This is what gives rise to new viral variants such as the ones that have emerged recently.
Some viruses have genetic codes of DNA, the same molecule that carries the genetic information in human cells. Other viruses, including the coronavirus, are based on a related molecule known as RNA.
Most RNA viruses lack a molecular proofreader, a protein that checks for mistakes and corrects them, so they “accumulate more typos more quickly," said Ms. Steinberg of the Feinstein Institutes for Medical Research. Coronaviruses, including the one that causes Covid-19, do have one and so tend to mutate more slowly.
Having a proofreader also makes coronaviruses three times the size of most RNA viruses, said Vineet Menachery, a coronavirus expert at the University of Texas Medical Branch. That gives them an advantage, he added: “It means they can encode more proteins to antagonize the immune response."
Some scientists believe the new variants, which have a large number of mutations, arose in Covid-19 patients whose weakened immune systems allowed the virus to reproduce over long periods of time—giving it plenty of opportunities to accumulate multiple mutations.
High rates of infection in the population also add to the risk that new, potentially more harmful variants will emerge, infectious-disease experts say. And with the virus spreading quickly around the world, experts say they expect to see more variants crop up.
What about the mutations seen in the new variants?
The new variant that cropped up in the U.K. has about two dozen separate mutations, including some related to the prominent outcroppings that stud the coronavirus’s outer surface. It is this so-called spike protein that helps the virus infiltrate cells by binding to and then breaching their outer membranes.
In theory, a mutated form of the spike protein could boost the ability of a virus to attach to cells and thus enable it to infect with increased efficiency. Previous research has shown one mutation of note in the U.K. variant can make the virus more infectious, said Dr. Ravindra Gupta, a University of Cambridge virologist who ran the studies.
The South African variant has more than 20 mutations, including several affecting the spike protein. Some are in key spots where antibodies that prevent the virus from entering cells bind, scientists said, meaning they could potentially help the virus evade a person’s natural immune response.
The U.K. and South Africa variants share a spike-protein mutation that enables the spike to bind more tightly to the cell membranes, research suggests.
A new variant has also surfaced in New York, called B.1.526. There are two versions of this variant, researchers say—one with a mutation called E484K in the spike protein and another with a spike protein mutation called S477N.
Scientists have shown that the E484K mutation, also seen in the South African variant and a variant in Brazil, can render the virus resistant against certain antibodies. The other mutation, S477N, could affect how well the virus binds to human cells, scientists say.
Researchers from the California Institute of Technology say the variant appeared in New York in late November and accounted for around 25% of coronavirus genomes sequenced in New York in February.
“It was only a matter of time before some variant was going to surface in New York," said Theodora Hatziioannou, a Rockefeller University virologist who is studying the new variants. “As cases go up in places, you observe variants going up as well."
She said it is too early yet to say how the New York variant will affect vaccine efficacy or reinfection rates. Nevertheless, “people should be careful even if they’ve gotten the vaccine," she said. “Masks and social distancing should still be observed until a significant proportion of the population has been vaccinated."
Do existing vaccines work against new variants?
A Pfizer Inc. laboratory study found its vaccine, developed with BioNTech SE, works against coronavirus mutations identified in the variants identified in the U.K. and South Africa. The antibodies generated by the vaccine were slightly less effective against mutations in the variant identified in South Africa, according to the study. The research is still preliminary, however. Pfizer’s study was conducted in a lab and tested only a subset of mutations found in the variants, but not the variants themselves.
Moderna Inc. has said its Covid-19 vaccine appeared to protect against emerging variants of the coronavirus in laboratory tests, but as a precaution it would test whether a booster shot improves immune responses and develop a new vaccine targeting the strain first identified in South Africa.
The findings are consistent with other preliminary results reported in recent weeks by several research groups looking at the effectiveness of available vaccines against the new variants.
For the U.K. variant, that confidence has been bolstered by recent preliminary studies, including one by BioNTech and Pfizer researchers showing that antibodies in the blood of vaccine-trial participants were effective at binding to the new variant’s mutated spike protein.
“Pfizer and BioNTech are encouraged by these early in vitro study findings," Pfizer said in a Jan. 20 statement.
For the variants found in South Africa, which have a different constellation of mutations, scientists are more concerned.
The mutations “raise some questions about vaccine efficacy, but it’s important to note that the vaccines elicit a broad immune response…that targets several areas of the spike protein," said Dr. Richard Lessells, an infectious-disease specialist at the University of KwaZulu-Natal in Durban, South Africa, and a member of the team that discovered the South African variant.
Pfizer and Moderna have conducted lab tests of their vaccines against several versions of the coronavirus and found that the vaccines were effective against all, according to the drugmakers.
The Centers for Disease Control and Prevention continues to urge people who are eligible for vaccination to get the shots. “Based on studies with other viruses containing similar mutations, CDC believes there will be little or no impact on immunity from natural infection or vaccination," the agency said in December.
The agency said on Jan. 22 it had reached out to public-health agencies in the U.K. to learn more about the risks the variant poses and that it continues to closely monitor the situation.
How will scientists know for sure if these new variants spread more easily?
Scientists said that they had studied some of the new variants’ individual mutations but that it would be important to look at what happens when they appear together—as they do in the new variants. That research involves experiments in cells and in animals to test whether the new variants attach to and enter cells more efficiently; whether they replicate more readily; and, most important, whether they spread more easily. Scientists have begun to do some of that work already, with more experiments planned for the coming weeks.
Animal studies involving an earlier coronavirus variant convinced some scientists that its particular mutations made it more infectious, said William Hanage, a Harvard T.H. Chan School of Public Health biologist who specializes in infectious disease. That version of the virus also had a mutated spike protein.
What can be done to stay safe from the new variants?
Infectious-disease experts and public-health officials say it is important to continue to adhere to the familiar strategies for avoiding contagion, including social distancing, masking and hand-washing, as well as avoiding exposure to others indoors, especially where ventilation is poor. Extra care might be required in indoor gatherings if experiments confirm that the new variants are more infectious.
Joanna Sugden and Betsy McKay contributed to this article.
This story has been published from a wire agency feed without modifications to the text
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