Rapidly spreading in countries worldwide, the 'delta variant' is under the global microscope as scientists assess the risk the highly transmissible strain poses to eliminating COVID-19.
Originally a variant of interest, B.1.617.2, now known as the delta variant of concern under the World Health Organization's , surfaced in Canada earlier this year. In April, incoming passenger flights from India and Pakistan were banned in an effort to curb the spread of the highly transmissible strain.
Experts say the delta variant spreads more easily because of mutations that make it better at latching onto cells in our bodies. In , the variant is now responsible for 90 per cent of all new infections. In the U.S., it represents 20 per cent of infections, and health officials say it could become the country’s dominant type as well.
South of the border, Dr. Anthony Fauci, the United States' top infectious disease expert, told reporters in a on June 22 that the delta variant's "transmissibility is undeniably greater."
Similar to the United Kingdom, "the delta variant is currently the greatest threat in the U.S. in our attempt to eliminate COVID-19," he said, adding that the "good news" is that the "vaccines are effective" against the highly transmissible variant.
But a mutation of the delta variant has medical officials around the globe increasingly concerned.
How much of a risk does the delta variant pose?
Dr. Jeffrey Joy, Assistant Professor, Department of Medicine at the University of British Columbia (UBC), told Â鶹´«Ã½Ó³» in an interview that he wholeheartedly agrees with Fauci's sentiment.
"In this case, we can kind of look across the water and see that despite a well-vaccinated population in the U.K. the delta variant is causing a surge in cases," he said.
"It is at least possible that that can happen here."
In terms of transmissibility, Joy underscored that the delta variant is significantly more transmissible than other strains. If the alpha variant (originally discovered in the U.K), for example, is approximately 50 per cent more transmissible than the original strain discovered in Wuhan, then the delta variant is close to twice that amount.
"The take-home message is that it is far more transmissible than the alpha. This variant can spread anywhere where there's an unvaccinated population," he explained.
"I 100 per cent agree with [Fauci]," he added. "If the delta variant reaches a high frequency then what we've set up is the perfect opportunity for the [delta plus] to arise here.
"Evolution works best in a large population."
What makes the delta plus mutation different?
The delta variant has 10 different mutations in the spike protein, relative to the original coronavirus (COVID-19) strain, explains Joy. "And in particular, it has three that make it easier for the virus to attach to the ACE2 receptor which is a receptor on our human cells that allows it to infect ours cells more easily, particularly for mutations."
The delta plus variant has an additional mutation in this spike protein, and that mutation is called K417N: "K amino acid — 417 is the number referring to the position in the sequence. And then N is the change to the amino acid."
Also seen in the beta variant (originally discovered in South Africa), the particular mutation confers immune evasion properties. "So the big concern with the delta plus variant is it's super transmissible because it has all the same mutations as the Delta variant, but it also has that plus mutation in the spike protein that also makes it more immune evasive."
Does that make the delta plus more transmissible?
Dr. Sarah Otto, UBC Professor, Department of Zoology at UBC, told V.I.A. that it is too early to tell whether "delta plus differs from delta in any significant way."
"The one genetic change that it does have in spike (N417K) is known to evade some monoclonal antibodies in lab assays, so we expect it to have some different immunological properties," she explains.
"But given that our bodies produce many different antibodies – and T and B cells – to various different parts of the virus (spike in the case of the mRNA viruses), the fact that a single (monoclonal) type of antibody fails doesn’t necessarily mean that delta plus is much worse than delta."
Dr. Horacio Bach, Adjunct Professor, Division of Infectious Diseases, Faculty of Medicine, UBC, told V.I.A. that there haven't been enough studies done on the delta plus variant — but that doesn't mean that the original delta variant or the mutation don't pose a threat.
"We need to be very alert. In my opinion, it will be a question of time before it takes over the previous one [alpha]," he explained.
"We don't know if delta will be the dominant or not but we know that younger people are infected with it and the symptoms are a little different from the original Wuhan strain."
While people were losing their sense of smell with the original strain, this strain has more flu-like symptoms, said Bach. While there haven't been enough studies yet, he noted that some "people are losing their hearing for a while." However, these new findings are still under investigation.
Get your second dose of a vaccine
Bach also notes that vaccine protection is lower with the delta variant. "At this point, we know the protection is less but still the vaccination of two doses is still giving you protection" and preventing serious illness, he said. As a result, it is critical people get both doses of a vaccine.
Researchers in England studied how effective the two-dose AstraZeneca and Pfizer-BioNTech vaccines were against it, compared with the alpha variant that was first detected in the U.K.
The vaccines were protective for those who got both doses but were less so among those who got one dose.
With files from the Canadian Press and the Associated Press.
