What Variant, Strain, and Mutation Mean When We Talk About COVID

Over a year into the coronavirus pandemic, fears no longer only surround the spread of the virus but also its new forms, or variants.

These include B.1.1.7. from the U.K., which was detected in September and became the dominant variant in England, partly prompting a third nationwide lockdown. Early evidence suggests it is more deadly and infectious than past forms of COVID.

South Africa's 501Y.V2 or B.1.351 variant, which shares some mutations with the U.K.'s, was first reported in December and is thought to be more infectious than previous types of COVID. Other variants being monitored by scientists include P.1, known as the Brazilian variant, and one from Denmark linked to mink.

The U.S. has reported cases of three new variants, including 541 of B.1.1.7 in 33 states, three cases of B.1.351 in two states, and two cases of P.1 in Minnesota.

News reports on these variants often use that term, as well as "strain" and "mutation." So, what do they mean?

What is the difference between a variant, strain and mutation?

As shown in the illustration below, COVID is made up of genetic information wrapped up inside a protein shell. Viruses like COVID need a host—like a human—to replicate and spread.

Mutations sound scary and unusual, but viruses often take on these tiny changes to their genetic information when they replicate. It's like making a mistake when using a pen to note down information from a whiteboard onto a piece of paper.

coronavirus, covid, virus, stock, getty
A stock image shows an illustration of COVID. Getty

The way COVID carries its genetic material means it is what is known as an RNA virus. COVID has fewer mutations than other RNA viruses because it can correct some of the mistakes made during replication.

Variants and strains occur when a virus collects significant mutations. These terms are often used interchangeably. But a variant becomes a strain when it has a "demonstrably different" phenotype, or characteristics, according to the authors of a recent article outlining the differences in the journal JAMA.

Ian Jones, professor of virology at the U.K.'s University of Reading, told Newsweek the most appropriate term to use when describing the new forms of COVID, like those from the U.K. and South Africa, is "variant."

The difference between a strain and a variant is "a matter of the degree of change but there is no magic level (10 percent overall is sometimes used) so there is some uncertainty about it," he said.

Explaining how they differ, Professor Tom Connor of the School of Biosciences at Cardiff University said, according to The Independent, "There is one strain of coronavirus. That is SARS-CoV-2. That is the single strain, and there are variants of that strain. These are variants."

He said: "The correct term to use is variant to describe this particular variant of concern."