Alpha, Beta, Gamma, Delta — there have been four Covid-19 variants of concern that have altered the course of the pandemic at different points in the past year and a half.
First came the Alpha variant, first detected in Kent, UK, that was more transmissible and caused the surges behind the winter wave of the pandemic. The Beta variant came next, triggering outbreaks in South Africa, along with Gamma, the variant that took hold of Brazil in January.
Now we have Delta ― definitely more transmissible, potentially more virulent (though it’s hard to know for sure), and a huge problem for those who remain unvaccinated.
Every day brings new concerning headlines about this variant or that mutation, which brings up the natural question: What’s next?
How SARS-CoV-2 has been evolving
To better understand what the next round of variants might look like, we need to take a look at what we’ve learned so far about how this coronavirus changes.
Each time the virus infects a new cell, it starts to makes copies of itself — and as it copies, it makes random changes (known as mutations) all over the place. Most mutations aren’t useful and die out, but some can be tolerated and passed on, said Ben Neuman, chief virologist at Texas A&M University’s Global Health Research Complex. Coronaviruses are typically slow changers — they mutate, as any virus does, but they don’t evolve at an alarming rate.
What shocked scientists is the rate of evolution, or how quickly these variants of concern acquired new mutations, according to Nathan Grubaugh, an evolutionary virologist and associate professor of epidemiology at the Yale School of Public Health. In general, the coronavirus goes through about one to two transmission cycles a month. But the variants of concern have acquired many more mutations much more quickly. Alpha, for example, didn’t just acquire one or two mutations, it picked up 17.
The leading hypothesis is that it took a prolonged infection ― probably in an immunocompromised person whose body had a tough time clearing out the virus ― to collect this many mutations so rapidly. From there, the virus spread to somebody else before taking off and shooting through entire communities.
According to Grubaugh, the same sort of rapid increase in mutations was identified with the Beta variant detected in South Africa and the Gamma variant that popped up in Brazil. “This phenomenon that we’re watching, of these variants that arise very quickly, I think caught a lot of us off guard,” Grubaugh said.
We’re going to see more variants
It’s impossible to predict exactly what future variants will look like, but it’s pretty undeniable that we are going to see new variants emerge.
“We haven’t seen the end of variants and we certainly haven’t seen the end of variants that are more transmissible,” Grubaugh said.
The development of new variants that rise to the level of concern is actually extremely rare. There have probably been hundreds of thousands of events where a host of new mutations have occurred, but those versions of the virus weren’t very fit so they died out before becoming a variant of concern. Just because the virus evolves, doesn’t mean it’s going to become a variant of concern.
But, when you give the virus so many different opportunities to infect new people, it will inevitably test out new variations. As long as there are people for SARS-CoV-2 to infect, the coronavirus will continue to evolve.
“We know that most of the variants we see emerge from people who are not vaccinated,” said Dirk Dittmer, a virologist at the University of North Carolina’s School of Medicine who is currently working on a variant tracking project in North Carolina.
We’ve never seen anything like SARS-CoV-2 before. We’ve never had a pandemic of this scale with so much global mixing. A variant that pops up in Brazil can be in Japan or the United States in a moment’s notice, Grubaugh said. What happens around the globe is going to impact the rest of the world — we aren’t living in a vacuum. This makes it a lot harder to predict what’s going to emerge and where.
What will those variants look like?
All that said, the scientists who study the evolution of viruses have some theories.
Grubaugh said the next generation of variants could be just like Delta, but better at what they do — probably more transmissible, maybe a little bit more successful at reinfecting people who were previously diagnosed with Covid-19. (We know the vaccines produce a more robust immune response than natural infection does.)
Neuman predicts somewhat the same. In July, scientists identified that 90% of the SARS-CoV-2 genomes were in the genetic group that fell under the Delta variant. Because of that, “the most likely bet is that future strains will look like Delta, but with extra changes,” Neuman said.
Gamma and Delta both are slightly better at evading immunity compared to Alpha and the other earlier variants. To Neuman, it seems reasonable to speculate that the current versions of the vaccines we’re using will eventually be less effective against newer variants.
Dittmer suspects future variants will become even more transmissible than Delta, but he also thinks they’ll cause symptoms that are less severe and are more in line with the common cold. “The virus just wants to infect as many people as possible and the best strategy for that is to make them as little sick as possible,” Dittmer said.
Much of this likely won’t be due to the virus itself, Grubaugh added, but because of rising levels of immunity to SARS-CoV-2 in one way or another — more vaccinations and greater levels of immunity from natural infection. This is generally how it goes with other viruses (think mononucleosis). They spread, but people with immunity don’t have as rough a go.
“The outcome that we see is that the infections will be milder,” Grubaugh said.
“The key to stopping new variants is to vaccinate so thoroughly that SARS-CoV-2 is not able to find enough new hosts to sustain itself.”
- Ben Neuman, chief virologist at Texas A&M University’s Global Health Research Complex
As the virus changes, our response changes
According to Grubaugh, one of the most important things to understand is that things change and we have to be ready for those changes. It’s not that the science or our understanding of Covid-19 has changed — the virus has changed.
“The key to stopping new variants is to vaccinate so thoroughly that SARS-CoV-2 is not able to find enough new hosts to sustain itself,” Neuman said.
We aren’t there yet with vaccinations across the globe, but we do have the tools. On top of that, scientists are already actively studying boosters so in the event a new variant comes around that outsmarts our current vaccines, we’ll be ready to go.
No one can completely predict what is really going to happen, Dittmer said. Variants are important, and as we’ve seen with Delta, they can really alter the course of the pandemic. But our vaccines are effective.
Ultimately, we’ll need to treat and respond to each new variant as it is. We know that Delta is more transmissible, so we need to fight transmission. If a future variant impacts vaccine efficacy, then we will address that with boosters.
“We have to address each problem as they arise and look forward to what might happen — and that’s why we’re working on boosters,” Grubaugh said.