The virus that causes covid-19 has mutated again and again, and experts say new variants will continue, in part because of the nature of the virus and also because large swaths of the population choose not to be vaccinated.
“Should we expect more variants? The answer is yes,” said Dr. Mohamed Yassin, director of infection control at UPMC Mercy. “How many? Probably too many. There will be a lot of them.”
The very nature of the coronavirus, he said, makes it susceptible to mutating.
There are two main types of viruses, Yassin explained: the DNA type and the RNA type. Every time the DNA virus divides, it makes an exact copy of itself. That perfect-copy process doesn’t happen in RNA viruses, meaning there is a chance for change each time the virus replicates. The virus that causes covid-19 is an RNA virus. So is influenza.
“It’s not different than what we see with the flu virus every year,” said Dr. Carol Fox, chief medical officer of Excela Health. “It changes often, and that’s why we need to get a new flu shot annually: because there are different variants that exist.”
Whether a variant will be more severe or more transmissible is, for the most part, up to chance, Yassin said. Viruses oftentimes can be changed or reengineered in a lab, he said, “but in nature, these changes are random.
“It’s almost impossible to know what is the next strain going to be,” he said. “Is it going to be more virulent or less? I don’t think we can know that.”
Potentially exacerbating the issue, Yassin said, is the fact that many people are not vaccinated.
Nationwide, just under 222 million people are fully vaccinated — about two-thirds of the population. About 47% have received one booster dose, according to the Centers for Disease Control and Prevention.
In Pennsylvania, about 66% of the population is fully vaccinated, and 32% have one booster dose, according to the state Department of health.
The portion of people vaccinated in Allegheny County is higher than it is across the state: 73% are fully vaccinated,
and nearly 38% have one booster dose, data show. In Westmoreland County, the numbers are lower than the state as a whole: 60% are fully vaccinated and 30% have received a booster.
“If you don’t have much (virus) going around, you’re going to have way less chance for mutation and new variants — that’s absolutely true,” he said.
He said that is an important part of the public health messaging that has and continues to go along with the pandemic.
“It’s not all about the person or you or me. It’s about us,” he said. “So, yes, if we all don’t get the infection, if we all have much less activity around because of vaccination, the rate of mutation will reduce for sure.”
Variants over time
There have been at least five variants of the virus identified, some of which had their own subvariants. Right now, omicron and its subvariants are the dominant strain circulating around the world. The first covid-19 case attributed to the omicron variant was detected in the United States in early December, and it proved even more transmissible than its highly infectious predecessor, delta.
The omicron variant was subsequently named a variant of concern, which the World Health Organization defines as a variant that shows an increase in transmissibility or detrimental change in covid-19 epidemiology; an increase in virulence; or is less affected by public health measures like vaccinations and mitigation measures.
Omicron led to the massive spike in cases in late 2021 and early 2022. While found to cause less severe illness than past variants, its quick and easy transmission meant an influx of hospitalizations and rise in deaths.
Since then, a number of omicron subvariants have been detected, including BA.2 and BA.2.12.1. In early June, the subvariants BA.4 and BA.5 were estimated by the CDC to make up about 13% of new cases — up from 7.5% the week prior, according to Yale Medicine.
Before omicron, there was the delta variant. It was first identified in Indiana in late 2020, according to Yale Medicine, but its U.S. surge did not begin until fall 2021, driving cases upward after months of decline. Some studies suggested the delta variant was 80% to 90% more transmissible than previous variants, and it was found to cause much more severe disease in those who were vaccinated.
The alpha, beta and gamma variants circulated in 2020, each with varying degrees of higher transmissibility. They were named variants of interest by the World Health Organization at the time.
The World Health Organization has also named a number of what they call variants of interest: variants that show predictable changes and cause significant community transmission. Among them have been epsilon, zeta, eta, theta, iota, kappa, lambda and mu.
“We didn’t call those variants of concern, but they were variants that were more transmissible,” said Dr. Kevin McCarthy, an assistant professor of molecular genetics and biology at the University of Pittsburgh. “What we saw as immunity started to build in populations, the viruses were able to make mutations and start to get past some of that immunity.”
How exactly that happens, he said, isn’t entirely clear.
“The virus is going to adapt as it passes its way through hundreds of millions and billions of people — going on and infecting and then reinfecting people,” said McCarthy, who is a member of the Pitt Center for Vaccine Research. “So anything the virus can do that allows it to do that better, it’s going to eventually figure out how to do those things.”
It’s a process that experts still don’t fully understand, he said.
It’s possible — but not certain — that some mutations happen in people with impaired immune systems who have persistent infections. As the body is trying to fight the virus, McCarthy explained, the virus is trying to replicate. To achieve that goal, the virus can evolve to infect cells more efficiently, he said, and can even evolve to evade antibodies created during the illness.
He likened it to playing the lottery every week.
Every time the virus replicates, it buys a lottery ticket. Most of the time, nothing comes of it, he said, “but every once in a while, somebody wins the Mega Millions.”
to be living with this’
As has been the refrain since the pandemic began more than two years ago, experts say there is no way to know exactly what the future holds.
“That’s the million-dollar question,” McCarthy said.
What he does know is that there is no indication that covid-19 is going away.
“We are going to be living with this,” he said. “What that looks like, I think we’re still really unsure.”
McCarthy said it’s not clear whether the virus will be seasonal like the flu has been in years past, but there will likely be surges and dips dictated by human behavior.
He said the best-case scenario would be one or two dominant variants at a time as opposed to myriad mutations making the rounds. That, he said, would make it harder to figure out how to handle the virus in the long term. For now, companies are working on covid vaccines that are in the same vein as flu vaccines in that they target three or four strains in one dose.
Fox said she believes that covid-19 eventually will look more cyclical.
“I think the hope is, or what you would expect to see, is those peaks and valleys getting smaller,” she said. “Instead of … high highs and low lows, the variations will continue, but they will look more like little blips.”
That is dependent upon human behavior, she noted. She said that’s why colds and cases of the flu generally begin in the fall when kids are back in school and more people are indoors for longer periods without windows open.
“It has to do with what’s going on in our environment,” she said. “There’s more opportunity for germs and viruses and bacteria to spread.”
Yassin, too, said he believes the virus could take on a more seasonal appearance, but noted that the real future of the illness, hospitalization and death from covid hinges on vaccinations.
“The rate of vaccination in the United States is really much lower than other Western countries,” he said. “That puts us in a more vulnerable position. We had, as the United States, so many cases, we had so much mortality. I wish we could convince more people to get their vaccine for their own sake and for the community’s sake, as well.”