TL;DR: Great question! There are new variants emerging all the time. It’s a normal part of viral evolution.
They compete by infecting people and making copies of themselves. Because of exponential math, even a small transmission advantage can quickly add up.
This all goes back to evolution and math. Here’s how it works. A virus replicates by infecting a person and making A LOT of copies of itself. This copying process is imperfect so that some of the copies have small differences from the original. RNA viruses, like the one that causes COVID-19, have some of the most error-prone replication processes on Earth. Scientists have a name for viral copies with changes – “mutants”. But they’re not from the blue lagoon…they’re just typos.
As a person’s infection progresses and these typos accumulate, they end up hosting a collection of closely-related viruses, sometimes called a “quasi-species cloud”. Most of these viral variants survive and reproduce about as well as any other. The changes don’t make any difference – the changes are “neutral.” But some end up with changes that make them better at doing what viruses do – infecting cells and replicating. This is how new variants emerge, and it’s happening all the time. More people being infected across the world mean more chances for variants to emerge. This means there can often be two or more variants of COVID-19 circulating in a country at same time if they reproduce at roughly the same rate. Scientists are keeping track, but for the rest of us, it doesn’t usually make a big difference.
But occasionally, a new variant comes along that is *way* better at causing new infections. For example – the now famous Delta variant. It’s looking like the new Omicron variant may have a transmission advantage as well. The World Health Organization designates these types of variants VOC (Variants of concern). A more transmissible variant will displace other circulating variants by infecting more people more quickly.
Remember that exponential growth we learned about early in the pandemic? This math applies to variants as well – a variant that is twice as transmissible as another becomes exponentially more prevalent very quickly. Early in a pandemic, variants that have any transmission advantage will quickly win this race because there are so many susceptible hosts. As more of the population gains immunity through infection and vaccination, variants that are able to get around immunity might spread fastest even if they’re not inherently more “infectious”. This *might* be what is happening with Omicron – it seems to infect easily AND infect people who have been previously infected or vaccinated, giving it more potential hosts.
Our best defense against the emergence of new variants is preventing infections everywhere in the world. So – get vaccinated. Get your booster. And advocate for policies that ensure vaccine access in all the world’s nations.
*Thanks to today’s guest writer, Epidemiologist and Nerdy Girl Dr. Jessica Williams-Nguyen! 🙏
Previous DP posts:
“Do COVID-19 vaccines promote the emergence of new variants?
“How and why do viruses mutate?”
Links:
Donate to GAVI global COVID vaccine fund
“What the Future May Hold for the Coronavirus and Us”
“Beyond Omicron: what’s next for COVID’s viral evolution”
“The Omicron variant can likely outcompete Delta — and that could worsen the U.S. Covid-19 epidemic
Twitter thread on variant competition from Dr. Trevor Bedford
