New Covid-19 strains: What scientists know about coronavirus variants

Meanwhile, in South Africa, doctors and researchers struggling with a second wave of Covid-19 cases are studying another new variant and what role it plays in raising the wave of cases there. The variant, known as B.1.351, has been identified in samples dating from October. It was not detected in the United States

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 appear as a result of small changes in its genetic code. During the pandemic, there were several variants. Those who have proven able to spread more effectively have become more widespread, while others are disappearing. “It’s just like natural selection, like evolution,” said Bettie Steinberg, a virologist and head of the Feinstein Institute for Northwell Health Research.

Why worry about these particular variants?

Some doctors worry that new variants of the coronavirus could overload the spread of Covid-19, putting additional stress on hospitals and nursing homes as cases approach their all-time highs.

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

Researchers at the London School of Hygiene and Tropical Medicine combined behavioral and epidemiological data on disease transmission models 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.

Contact tracking data in the UK show that patients infected with the new variant continued to infect more people than those infected with previous variants. The 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.

Is it possible that the rapid spread of new variants is not the result of increased infectivity, but instead of weak adherence to social distancing and other measures aimed at reducing contagion?

Scientists do not believe, at least in Britain. As proof, Prof. Neil Ferguson, an epidemiologist at Imperial College London and a member of a scientific group advising the British government on respiratory virus threats, showed epidemiological data from November showing that cases of the new British variant were exploding in the south. east of London, as coronavirus cases were falling in other parts of the country. The whole country was blocked during this period.

The situation may be different in South Africa, where researchers said human behavior could play a key role in increasing cases. Millions of South Africans have traveled extensively in recent weeks, and tens of thousands have gathered in restaurants and bars and on beaches during the holiday season.

What gave rise to the new variants?

Like other viral pathogens, coronavirus spreads by infecting cells and then reproducing inside them, creating copies of it that spread throughout the body and then are shed, potentially infecting other people.

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

Some viruses have genetic codes of DNA, the same molecule that carries genetic information from human cells. Other viruses, including coronavirus, are based on a related molecule known as RNA. RNA viruses do not have a molecular corrector, a protein that checks for mistakes and corrects them, so they “accumulate more mistakes faster,” said Dr. Steinberg.

But the mutations observed in the new variants?

The new variant that appeared in the UK has about two dozen separate mutations, including some related to prominent outcrops that study the outer surface of the coronavirus. This so-called spike protein helps the virus to infiltrate cells by binding and then violating their outer membranes.

In theory, a mutant form of spike protein could increase a virus’s ability to attach to cells and thus allow it to become infected with increased efficiency. Previous research has shown that a notable mutation in the British version can make the virus more infectious, said Dr. Ravindra Gupta, a Cambridge University virologist who conducted the studies.

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

Variants in the UK and South Africa share a protein mutation that allows for closer binding of cell membranes, research suggests.

Do existing vaccines work against the new variants?

Although there is not yet a final word on the existing vaccine made by Pfizer Inc.

and BioNTech SE and Moderna Inc.

confers immunity to new variants, scientists have expressed confidence that they do.

The mutations “raise some questions about the effectiveness of the vaccine, but it’s important to remember that vaccines generate a broad immune response … targeting more areas of the spike protein,” said Dr. Richard Lessells, a specialist in infectious diseases at the University of KwaZulu -Born in Durban, South Africa, and a member of the team who discovered the South African variant.

Pfizer and Moderna performed laboratory tests of their vaccines against several versions of the coronavirus and found that the vaccines were effective against all, according to the drug manufacturers. The companies said they were conducting experiments to determine if the antibodies generated by the vaccinated people were effective against variants in the UK and South Africa.

The Centers for Disease Control and Prevention continues to urge people who are eligible for vaccination to receive photos. “Based on studies with other viruses that contain similar mutations, the CDC believes there will be little or no impact on immunity to natural infections or vaccinations,” the agency said in a statement Tuesday.

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

The scientists said they 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 cell and animal experiments to test whether new variants attach and enter cells more efficiently; if they reproduce more easily; and, most importantly, if they spread more easily.

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

What can be done to avoid new variants?

Infectious disease experts and public health officials say it’s important to continue to follow familiar strategies to avoid infection, including social distancing, masking, and hand washing, as well as avoiding exposure to others indoors, especially in ventilated areas. he is poor. Additional attention may be needed in indoor meetings if 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]