Variant or ‘Scariant’: When to Worry About Covid Virus Strains
Plus, the most important way to prevent more variants from emerging
Although the word “mutation” often conjures frightening associations, such as three-headed fish or The Andromeda Strain, in reality, mutations are simply changes that arise in DNA or RNA. Reproduction is one opportunity for these changes to emerge, creating the starting material for evolution, including in viruses. In this way, as researcher Nathan D. Grubaugh and colleagues wrote back in March 2020, mutations are just “a humdrum aspect of life for an RNA virus.”
But recent reporting about mutated variants of the SARS-CoV-2 virus has understandably caused some anxiety. When the data don’t confirm reasons to worry, Eric Topol, MD, professor of molecular medicine at Scripps Research, has coined a term for these variants: “scariants.”
But the concerns linger. Why do specific variants make headlines, and how much do you need to worry about them? Here’s what you need to know.
What is a variant and why do they occur?
A variant is a version of the pathogen that contains mutations compared to a reference SARS-CoV-2 virus. The reference virus is typically the most common circulating one, and the variant differs from it but not so much so that it’s a different species, explains Angela Rasmussen, PhD, a virologist at Georgetown University.
Most mutations don’t matter from a human perspective, says Vaughn Cooper, PhD, a microbiologist and molecular geneticist at the University of Pittsburgh. Either the changes don’t affect the coronavirus or they harm it. But viruses with a mutation that gives them an advantage may come to dominate in an individual host. If the mutated version is transmitted to someone else, a variant is born.
Why are so many variants cropping up now?
“When infections are infrequent, there’s not as much opportunity for the virus to evolve,” Cooper says. But then case counts reached millions, so natural selection has a lot of variants to choose from. “It didn’t surprise us at that point that we started to discover them,” says Cooper, because every new infection is an opportunity for new mutations to crop up when the virus reproduces.
Scientists also are finding more variants because they’re actively looking for them. Initially, scientists were focused on understanding the disease and less so on sequencing viruses to track possible variants. U.K. researchers led the way in tracking the virus’s evolution from early in the pandemic. Once they found the “U.K. variant,” other countries stepped up their surveillance. The Biden administration announced in mid-February that it’s putting almost $200 million toward tracking new variants.
How often do viruses mutate?
Most RNA viruses — the type all coronaviruses are — make loads of mistakes when copying over their genetic sequences for reproduction, but coronaviruses have a “proofreading” enzyme to reduce the errors, says Susan Weiss, PhD, a microbiologist at the University of Pennsylvania who has studied these viruses for decades.
“This virus might be running out of big adaptations because they’re all basically grabbing the same handful.”
Still, mutations happen. The number of infections is a determinant of how fast. The more the coronavirus reproduces, or replicates, “the more opportunity it has to evolve,” says Weiss. But that proofreading enzyme makes the virus more stable than most. Current data suggests that the SARS-CoV-2 virus is accruing one mutation about every two weeks, Vaughn says.
Topol emphasizes the effects of several mutations existing in a single variant. Any single mutation, even if it gives the virus an advantage, is often benign on its own, he says. “It’s the interaction of these mutations on the virus that’s really important.”
A virus with advantages doesn’t necessarily make its host sicker. But it could spread farther, faster. The current variants actually have a lot in common and are converging on the same handful of mutations, Cooper says. That convergence “suggests this virus might be running out of big adaptations because they’re all basically grabbing the same handful,” he explains.
What does it mean for a variant to be more transmissible?
There are several ways a virus can evolve to pass more easily from person to person, says Rasmussen. Mutations could lead the virus to bind more easily or tightly to cells to enter them more quickly and begin replicating. Or a mutation could help the virus create more copies of itself or create copies faster. If a mutation leads to a higher concentration of SARS-CoV-2 virus in an infected host, more of them could be exhaled and passed onto others.
Mutations might also extend the infectious period — how long someone sheds the virus — or make the virus more stable and viable outside the host. Combinations of these changes are possible, too.
What hasn’t changed is what each person can do about them. “None of those things will change how a mask works,” says Rasmussen. “The virus didn’t suddenly acquire the ability to go through walls.”
How much should we worry about variants?
If you’re not a scientist, not so much. “One thing that might help people worry a little bit less is that there are thousands of variants of SARS-CoV-2 circulating in the population,” Rasmussen says, and only a handful are “variants of concern.”
Variants of concern must increase transmission, cause more severe disease, or be less susceptible to existing immunity or to vaccines, masking, drugs, and other public health measures. Experts have been monitoring three: B.1.1.7., known as the “U.K. variant,” B.1.351, which became dominant in South Africa, and P.1, which caused a resurgence in Brazil.
Then there are “variants of interest,” those that scientists are just monitoring. The New York and California versions are “variants of interest” for now. Although the New York version may become a variant of concern, says Topol, the California variant isn’t ringing many alarm bells so far. In fact, early panic about that variant is a good reason to dial down the “variant mania,” he says, because there’s no evidence that it’s as worrisome as first reported.
Meanwhile, all three variants of concern have been detected in the United States, although none have become dominant. The variants B.1.351 and P.1 are both similar and bear the same concerning mutations. These changes help the virus avoid some existing antibodies to SARS-CoV-2 — from the vaccine or a past infection — and may help the virus bind to the cell more tightly.
“Worrying about it doesn’t help,” Weiss says. “What helps is wearing a mask and getting vaccinated.”
Because evidence suggests that these variants are more contagious, public health experts worry that this “increased contagiousness will hinder our ability to control [the pandemic] at our current rate of vaccination,” explains Cooper. Increasing contagiousness means a higher threshold for herd immunity. “We are literally in a public health race between trying to reach herd immunity and the virus evolving to evade public health control,” he says.
But that doesn’t mean the rest of us need to do anything different.
“Worrying about it doesn’t help,” Weiss says. “What helps is wearing a mask and getting vaccinated.”
Will the current vaccines work against the new strains?
It depends on how you define “work.” The vaccines were tested for their ability to prevent severe disease, hospitalization, and death. By that measure, all three currently authorized vaccines do that about as well against the U.K., Brazil, and South African variants as they do against other variants that have dominated. But the vaccines may not protect as well against infection or mild to moderate disease related to these newer variants.
“These vaccines are just towering miracle successes and so much better than what we could have possibly hoped for at the beginning,” says Cooper. With these newly emerging variants, “the vaccines work, they just don’t work as well.”
Neutralizing antibodies aid in preventing infection, and some research suggests that the mRNA vaccines induce fewer of these antibodies against the South African variant. But “antibody neutralization is not the same thing as vaccine efficacy,” Rasmussen explains, because vaccines can prep the immune system to fight off disease in other ways, too.
In addition, scientists can tweak the current vaccines to target a newly emerged variant, if needed. For now, though, the variant threat calls for vaccinating as many people as possible as quickly as possible. “Get the vaccines now,” advises Topol. “The vaccines may well override any concerns about immune evasion of the variants,” he says, noting that currently used vaccines already work well against the U.K. strain. The two mRNA vaccines (made by Pfizer and Moderna) have shown high efficacy against the South African variant, which has shown the most potential for dodging the immune system’s defenses.
As for the idea that the new vaccines drive the evolution of new variants that can infect vaccinated people, so far, no evidence suggests this is happening, says Rasmussen. It’s not an impossible scenario, but not enough people have been vaccinated to put that kind of pressure on the virus, she says, and the other experts agreed.
Will immunity from past infection protect me from the variants?
The body’s immune system is pretty amazing at adapting quickly to fighting different versions of pathogens it’s encountered before. Past infection is likely not as protective as vaccines, but it will offer some protection. As Bill Hanage, PhD, an epidemiologist at the Harvard T.H. Chan School of Public Health, tweeted, the variants that emerged from South Africa and Brazil “may well have some impact on the virus’s ability to reinfect, but that’s not the same thing as entirely evading the immune system.”
Is there any way to stop new variants from emerging?
Yes, we prevent new variants in the same way we prevent current variants from prolonging the pandemic: We stop the spread of the virus.
“The virus is evolving just like we thought it would,” says Cooper. Tracking it can inform public health strategies, but everyone else should focus on preventing new infections by masking, socially distancing, improving ventilation, and getting vaccinated when they can. “The pathway to success is minimizing infections.”