COVID-19 Resource Center

Viruses mutate and form new variants "to try to survive better," according to David Wohl, a professor of medicine who specializes in infectious diseases at the University of North Carolina School of Medicine.

Human immune systems create a lot of barriers for viruses to get through once they enter our bodies, Wohl said. Mutating is a matter of survival — the viruses that are able to get through those immune attacks, get out into the air, enter someone else's body and continue to spread will be the viruses that survive.

"Viruses are selected out for survival of the fittest," Wohl said. "And by fittest, that usually means more 'catchy.' Maybe it lasts longer in the nose and throat and can be spread to more people."

Viruses don't mutate to evade medicine and vaccines, but rather the human immune system, Wohl said.

"It's no surprise over the last year and a half, where we basically have done nothing to try to fight the virus except for vaccination, and most of the planet is far from being vaccinated, that the viruses are running amok and able to evade our immune systems more and more," Wohl said.

Wohl said the main changes in the SARS-CoV-2 variants are differences in the spike proteins, "the spiky part on the outside of the virus that attaches to receptors on our cells."

"The spike proteins can change in modest ways, but in ways that help evade a system that might have antibodies directed against the spike protein," Wohl said.

The variants can be "chameleon-like," he said. With different spike proteins, the antibodies from the vaccine or that the body makes against a previous version of SARS-CoV-2 won't recognize the virus and move on.

The four main variants of the SARS-CoV-2 virus, currently, are the alpha, beta, gamma and delta variants, but others exist.

The alpha variant was first detected in the United Kingdom in September 2020. It was first detected in the United States in December 2020. The beta variant was initially detected in South Africa in December 2020, and was found in the U.S. at the end of January. The gamma variant was initially identified in Brazil in early January, and was found in the U.S. that same month.

There are also other variants, such as the iota variant first identified in the United States and the lambda variant first seen in Peru, according to Wohl.

He stressed that the variants aren't necessarily from the places in which they're first identified.

Alpha became the dominant variant in the U.S. by April, and it remained that way through June. Now, the highly transmissible delta variant is the most common strain of the virus circulating through the country.

Wohl said there have been shifting variants of the virus since the beginning of the pandemic.

"We went from what we call the ancestral Wuhan variant to a variant that was somewhat different and might be a little more catchy," he said. "That just took a mutation to occur."

If the virus continues to spread, variants are going to keep popping up.

"As long as people are harboring the virus and replicating it, that's going to keep happening. That's the problem," he said. "Once you stop replication and spread, you're not going to have variants anymore."