Scientists have noted that the two new descendants of Delta appear to have a slight survival advantage and are somewhat more transmissible. This indicates that the SARS-CoV-2 virus may still have opportunities to continue adapting to humans.
Jesse Shapiro, an Associate Professor in the Department of Microbiology and Immunology at McGill University, stated: “It’s hard to say how far the limits are. They will continue to evolve to reach the highest level of adaptation.”
Sublineages developed from the Delta variant seem to have a slight survival advantage. (Illustrative image: Tribuneindia).
The two Delta sublineages, known as AY.25 and AY.27, were first detected in Canada during the spring. New cases have emerged in every province except Prince Edward Island.
AY.25 is becoming the prevalent strain of SARS-CoV-2 in Saskatchewan. In Ontario, AY.25 accounts for 31% of the 1,670 cases sequenced in the past four weeks.
The sublineages, developed from the Delta variant, seem to have a slight survival advantage. They are growing and spreading 5% faster. This rate is lower compared to Delta’s spread compared to Alpha (which spreads 40-60% faster).
Professor Shapiro added: “This is more or less what we expected, the virus will spread as reopening occurs, particularly in the western provinces this summer.”
Art Poon, an Associate Professor of viral evolution at Western University, explained that to understand the sublineages, one can think of SARS-CoV-2 as a large tree that continues to sprout as the virus evolves in different regions of the world.
The trunk represents the virus strain that emerged in Wuhan (China). Variants of concern like Delta and Alpha are akin to heavy branches because they differ significantly from the original strain, accelerating the spread of the virus or causing more severe illness. The sublineages resemble smaller branches.
“We need to discuss the specific parts of the tree, especially when the branches carry mutations that impact public health,” Poon assessed.
It remains unclear what makes the new branches slightly more transmissible. AY.27 has changes in the spike protein that the virus uses to enter human cells. Similar mutations have also appeared in AY.4.2, which has spread throughout the UK.
Professor Poon reported that there is currently no evidence that the two new variants can evade immunity.
Notably, the branch variants have been present in Canada for some time, at least since early April, but thanks to the efforts of the public through vaccination and mask-wearing, the number of Covid-19 cases has decreased in most regions. In April, the daily Covid-19 case count was around 8,000, and it has now dropped to approximately 2,000.
Thus, even with the dominance of Delta branch variants, there will not be a surge in case numbers, and everything will not change drastically.
The virus’s ability to evolve depends on the number of infections. The best way to reduce this number is to vaccinate as many people as possible. Currently, up to 75% of Canadians have received both doses of the Covid-19 vaccine.
