New strains of Covid-19: what scientists know about coronavirus variants

Meanwhile, in South Africa, doctors and researchers battling a second wave of Covid-19 cases are studying another new variant and what role it plays in the growing wave of cases there. The variant, known as B.1.351, was identified in samples dating from October. Not detected in the USA

Here’s 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. Throughout the pandemic, there were several variants. Those that have proven to be able to spread more efficiently have become more prevalent, while others have failed. “It’s like natural selection, like evolution,” said Bettie Steinberg, virologist and dean at the Feinstein Institutes for Medical Research at Northwell Health.

Why the concern with these specific variants?

Some doctors fear that new variants of the coronavirus may overload the spread of Covid-19, putting additional stress on hospitals and nursing homes when cases are close to their historic peak.

Preliminary data suggests that the new variants are no more likely to cause serious illness than the more familiar forms of the coronavirus. But even if its virulence is not greater, the apparently increased transmissibility of the variants could mean more misery and death, increasing the number of Covid-19 cases.

Researchers at the London School of Hygiene and Tropical Medicine have combined behavioral and epidemiological data on disease transmission patterns with mathematical models to determine whether the UK variant is more transmissible than previously identified variants.

They found that the new variant is more transmissible than the previous variants.

UK contact tracking data shows that patients infected with the new variant infected more people than those infected with the previous variants. The data also suggested that the viral load, or the amount of viruses 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.

Is it possible that the rapid dissemination of the new variants is not the result of an increase in infectiousness, but of a weak adherence to social detachment and other measures aimed at containing contagion?

Scientists don’t think so, at least in the UK. As evidence, Prof. Neil Ferguson, an epidemiologist at Imperial College London and a member of a scientific panel advising the British government on respiratory virus threats, pointed to epidemiological data from November showing that cases of the new UK variant were exploding in the south east area of ​​London, while coronavirus cases were falling elsewhere in the country. The entire country was confined during this period.

The situation may be different in South Africa, where the researchers said that human behavior may be playing a key role in the increase in cases. Millions of South Africans have traveled extensively in recent weeks and tens of thousands have gathered in restaurants and bars and on the 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 inside them, creating copies of itself that spread throughout the body and are eliminated, potentially infecting others.

The reproduction process involves copying the virus’s genetic code, which contains instructions for building successive generations of viral particles, or virions. But the code is not always faithfully reproduced; sometimes the copying process produces errors that the researchers compared to typographical errors. This is what gives rise to new viral variants, such as those that have recently appeared.

Some viruses have genetic codes for DNA, the same molecule that carries genetic information in human cells. Other viruses, including the coronavirus, are based on a related molecule known as RNA. RNA viruses lack a molecular reviewer, a protein that checks for errors and corrects them, so they “accumulate more typos more quickly,” said Steinberg.

What about the mutations seen in the new variants?

The new variant that emerged in the UK has about two dozen separate mutations, including some related to the prominent outcrops that spread across the outer surface of the coronavirus. It is this so-called peak protein that helps the virus to infiltrate cells, attaching and breaking their outer membranes.

In theory, a mutated form of the spike protein could increase the ability of a virus to bind to cells and thus allow infection more efficiently. Previous research has shown that a major mutation in the UK variant could make the virus more infectious, said Dr. Ravindra Gupta, a virologist at the University of Cambridge who conducted the studies.

The South African variant has more than 20 mutations, including several that affect the spike protein. Some are at key points where antibodies that prevent the virus from entering cells bind, the scientists said, meaning they can help the virus prevent a person’s natural immune response.

The UK and South Africa variants share a peak protein mutation that allows the peak to bind more tightly to cell membranes, the research suggests.

Do existing vaccines work against new variants?

Although there is no final word yet on whether the existing vaccine made by Pfizer Inc.

and BioNTech SE and Moderna Inc.

to give immunity to the new variants, the scientists expressed confidence that they did.

The mutations “raise some questions about the vaccine’s effectiveness, but it is important to note that vaccines elicit a broad immune response … that targets multiple areas of the peak protein,” said Dr. Richard Lessells, an infectious disease specialist. from the University of KwaZulu -Christmas in Durban, South Africa, and member of the team that discovered the South African variant.

Pfizer and Moderna conducted laboratory tests of their vaccines against various versions of the coronavirus and found that the vaccines were effective against everyone, according to the manufacturers. The companies said they are conducting experiments to determine whether antibodies generated by vaccinated people are effective against variants in the UK and South Africa.

The Centers for Disease Control and Prevention continue to encourage people who are eligible for vaccination to get vaccines. “Based on studies of other viruses containing similar mutations, the CDC believes that there will be little or no impact on the immunity from natural infection or vaccination,” the agency said in a statement on Tuesday.

How will scientists know for sure if these new variants spread more easily?

The scientists said they had studied some of the individual mutations in the new variants, but that it would be important to look at what happens when they appear together – as they do in the new variants. This research involves experiments on cells and animals to test whether the new variants bind and enter cells more efficiently; whether they replicate more readily; and, most importantly, whether they spread more easily.

Animal studies involving a previous variant of the coronavirus have convinced some scientists that its specific mutations made it more infectious, said Dr. William Hanage, a biologist at the Harvard School of Public Health TH Chan who specializes in infectious diseases. This version of the virus also had a mutated spike protein.

What can be done to protect against new variants?

Infectious disease experts and public health officials say it is important to continue to adhere to family strategies to prevent contagion, including social detachment, masking and hand washing, as well as avoiding exposure to others in closed environments, especially where there is ventilation is poor. Extra care may be needed in internal meetings if the experiments confirm that the new variants are more infectious.

—Joanna Sugden contributed to this article.

Write to Daniela Hernandez at [email protected] and Sarah Toy at [email protected]