Variant or strain? Experts explain what's happened to the coronavirus
TORONTO -- A new, more contagious variant of the virus that causes COVID-19 that first surfaced in the U.K. and has now been detected in Canada, is changing researchers’ understanding of the virus including how to define and describe it.
While some have referred to this as a new variant, others are calling it a strain as well as a mutation. However, experts say these terms are not interchangeable and all of them don’t necessarily apply to this change in the virus.
Jean-Paul Soucy, a PhD student at the University of Toronto's Dalla Lana School of Public Health, explained to CTVNews.ca that the term strain is specific to the virus SARS-CoV-2, but not COVID-19 – the disease caused by it.
Soucy said in a telephone interview on Sunday that variant is the correct term to use when classifying a known virus that has developed a "specific group of mutations" that causes the variant to behave differently than that of the strain it originated from.
"A strain of a virus has distinct properties and a particular immune response. Then there's going to be lots and lots of variants which will be, in many cases, minor accumulations of mutations and different kind of genetic lines of that strain," Soucy said.
Soucy said a certain strain of virus is considered a variant when it has enough mutations to change a minor portion of its genetic code. He says the most recent variant found in the U.K. meets that benchmark.
This variant, known as B.1.1.7, spreads far more easily between people as a result of a series of mutations that have been identified in the genetic coding.
According to U.K. researchers, the B.1.1.7 variant is up to 70 per cent more transmissible because it has 22 coding changes to the virus genome. The new variant has since been found in other countries around the world, including Canada, France, Japan, Israel and Sweden.
However, Soucy noted that all currently known variants of COVID-19 belong to the SARS-CoV-2 strain and have not mutated enough to either be classified as their own strain or be ineffective against current and prospective COVID-19 vaccines.
EXPLAINING MUTATING VIRUSES
Dr. Gerald Evans, chair of Queen's University's infectious diseases division in Kingston, Ont., told CTVNews.ca that one of the major mutations seen in the variant is to that of the spike protein, which has enhanced how it invades human cells.
This protein is also what researchers have been targeting for vaccines and antibody-based therapies.
Evans explained in an email that this mutation, known as N501Y, seems to have helped the SARS-CoV-2 spike protein attach "more readily to the human cell receptor ACE-2."
"A mutation is simply the presence of a change in the nucleotide sequence of the RNA of the virus… that causes a change in an amino acid residue in a virally expressed protein," Evans said.
He added that this mutation to how the spike protein binds with human cells is likely why the variant is "more transmissible than others."
In addition to the B.1.1.7 variant, other mutations of the virus have recently been reported in South Africa and Nigeria.
Infectious disease expert Dr. Lisa Barrett told CTV News Channel on Sunday that viruses often mutate, but some viruses do it more than others. She noted that while the genetic code of coronaviruses does typically change over time, she says the mutations aren’t normally a cause for concern.
Barrett said in an interview from Halifax that health officials don’t have to note all variants of COVID-19, but do need to look at which ones may change who becomes infected with the virus, the symptoms, and how it responds to vaccines.
"We don't need to recognize every variant of this virus, but we do need to determine which ones are important, and that's a work that's going to take a month or two right now," she said.
Before the emergence in Britain of this more contagious variant, other COVID-19 variations were mostly benign, according to U.K. researchers.
Barrett says current data shows that COVID-19 vaccines will "likely work" against this new variant, but said more research needs to be done.
Until more is known about the B.1.1.7 variant, Barrett said current public health measures including physical distancing, wearing face coverings and frequent hand washing need to be maintained to help limit its further possible spread.
"The best way of doing this is making sure that we don't have a lot more cases, limit travel, hand wash, distance, mask -- we've got to stay at it for a while longer," Barrett said.