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SYDNEY (Reuters) – As the SARS-CoV-2 coronavirus spread around the world, killing more than 1.5 million people in the past year, it has morphed into seven major groups, or strains, as reported. adapted to its human hosts.
Mapping and understanding those changes in the virus is crucial to developing strategies to combat the COVID-19 disease it causes.
“The reason for looking at genomics is to try to figure out where it came from … in terms of trying to map what we would expect from the pandemic, that information is critical,” said South Australia health director Nicola Spurrier . he said after an outbreak in the state in early November.
Reuters analyzed more than 185,000 genome samples from the Global Initiative for Sharing All Influenza Data (GISAID), the largest database of novel coronavirus genomic sequences in the world, to show how the global dominance of major strains has changed over time.
The original strain, detected in the Chinese city of Wuhan in December 2019, is the L strain. The virus then transformed into the S strain in early 2020. This was followed by the V and G strains. The G strain mutated even more so in the GR, GH and GV strains. Several other rare mutations were collectively grouped as strain O.
(Reuters graphic: https://tmsnrt.rs/3n9197O)
MONITORING MUTATIONS
A mutation is a change in the genetic material of an organism. When a virus makes millions of copies of itself and moves from host to host, not all copies are identical. These small mutations build up as the virus spreads and copies itself over and over again.
At the beginning of the pandemic, the virus made its way relatively quickly around the world, repeatedly making its way into different locations and causing new outbreaks on a regular basis. During that time, there was a more diverse mix of strains among the samples reported to GISAID.
As countries began to close their borders, fewer new strains were introduced, and in countries where the most resistant type G strains were present, they began to dominate.
In Asia, the original L strain persisted longer as several countries, including China, rushed to close borders and restrict movement. By contrast, North America and Europe did not restrict movement as much, at least initially, allowing G strains to spread and mutate at a faster rate.
“This virus moves in super-spreading events, which means the virus doesn’t have to be particularly contagious,” said Catherine Bennett, chair of epidemiology at Melbourne’s Deakin University School of Health. “We will see different patterns due to group transmission.”
The G strains are now dominant throughout the world. A specific mutation, D614G, has become the most common variant.
The most recent mutation to emerge is the GV strain, which has so far been isolated in Europe, where experts say it is unclear whether the strain is spreading due to some transmission advantage or because it affected young adults and tourists socially. active during the summer.
WHY MUTATIONS MATTER
So far, the SARS-CoV-2 virus has slowly mutated, allowing scientists and policy makers to keep abreast of its progress.
Still, scientists have been divided over the implications of some of the mutations. Some experts have reported that the D614G variation has made the virus more transmissible, however other studies contradict this.
Either way, the changes so far have not resulted in strains that would likely be resistant to vaccines in development.
However, experts who have watched the influenza and HIV mutation for years, eluding vaccines, caution that future SARS-CoV-2 mutations remain unknown. And the best chance of avoiding changes that make the virus impervious to a vaccine remains to reduce its spread and reduce its chances of mutating.
“If the virus changes substantially, particularly the spike proteins, then it could escape a vaccine. We want to slow down the transmission globally to slow down the clock, ”said Deakin’s Bennett. “That reduces the chances of a one in a trillion change which is terrible news for us.”
(Reporting by Jane Wardell, Jitesh Chowdhury and Simon Scarr)
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