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In December, the UK reported a worrisome variant of Covid-19, commonly known as variant B117, which appeared to be more transmittable. Since then, scientists have established that B117 is between 50% and 70% more transmissible than other variants. If more people get sick, there is more pressure on health systems, and in the UK health services are so overloaded that a nationwide lockdown has been imposed.
While many scientists say that B117 does not appear any more lethal, researchers from the UK government’s New and Emerging Respiratory Virus Threat Advisory Group found that it can increase the death rate by 30-40%, although the size of the sample was small and they said more research is needed. necessary. With B117 now detected in more than 50 countries, it is urgent to understand the variant.
But other worrisome variants have also been identified, including in California, South Africa and Brazil.
So what exactly is a variant and how many are there? And why are some variants more worrisome than others?
Stuart Turville, associate professor at the University of New South Wales, who works with the Kirby Institute’s pathogenesis and immunovirology program, says that although many people have referred to some of these variants as new “strains” of the virus, it is more accurate to say that the strain of virus that causes Covid-19, known as SARS-CoV-2, has thousands of variants, which can also be described as subtypes, isolates or lineages.
However, some of these variants have more changes in their genetic instructions, known as the genome, than others. Turville says that the Covid-19 genome is around 30,000 base pairs. Base pairs are molecules on opposite strands of the virus’ genetic material, which form chemical bonds with each other. These chemical bonds act like rungs on a ladder and help hold the threads together.
“In the context of the variant identified in the United Kingdom [B117], there are about 24 changes out of those 30,000, so if you look at that in the context of the entire virus genome, it’s not a huge change from what it was at the beginning in 2020, “says Turville. However, there are still more changes than usual; other variants have only one or two changes, also called mutations, in the genome.
The variant identified in South Africa, named B1351, also has an unusually high number of mutations, including some of those seen in B117. Again, there is no evidence to suggest that this variant increases the severity of the disease, but it has become the dominant variant in Zambia and is therefore likely to be more transmissible, although research is ongoing.
“There have been thousands of different variants,” Turville told Guardian Australia.
“One of the things that virologists and molecular virologists say is that it is easier to break something than to turn it into something bigger, better and faster. There are many variants of viruses that have appeared and disappeared. If you remove a key item, it falls apart and is actually a very fragile virus.
“The key mutants we are talking about are the ones that survive the change and continue. They are the ones that start to outgrow the variants in the past, and that is what we are currently seeing in the UK and elsewhere. “
Another variant of concern, known as P1 or B1128, was first detected in January in travelers arriving in Japan from Brazil. It shares some of the same mutations as B1351, and generally has more than 20 changes, deletions, mutations, and insertions in its genome. A report by Brazilian researchers said it is “potentially associated with an increase in the transmissibility or propensity for reinfection of individuals.”
In other words, there is some concern that it may evade the antibody response in people with existing immunity to the virus, but much more work is needed to establish this. But since the researchers said that P1 appears to be associated with a rapid increase in cases in places where previous attack rates are believed to be very high, “it is essential to quickly investigate whether there is a higher rate of reinfection in previously exposed individuals.” .
Then, on January 17, the California Department of Public Health in the US revealed that a variant known as L452R is increasingly being identified by genomic sequencing in several counties in the state. However, the department said in a statement: “It is too early to know if this variant will spread more rapidly than others.”
“The fact that this variant has been identified in several large outbreaks in our county is a red flag and should be investigated further,” said Santa Clara County Health Officer Dr. Sara Cody.
Australian health officials are concerned that variants that are currently wreaking havoc in the UK, South Africa and Brazil could leak out of the hotel quarantine, where returning travelers must be isolated for 14 days and undergo testing.
On Friday, Deputy Chief Medical Officer Michael Kidd said if someone tested positive for the variants, they would have to undergo another 14 days of isolation before being released, compared to 10 days for people diagnosed with less worrisome variants.
There are a couple of theories as to why some variants managed to take hold while others died out, Turville said.
“In terms of the variants identified in Brazil and the United Kingdom and how they have appeared, there is evidence that people infected with the virus for a longer time accumulate more changes in the virus.”
Immunosuppressed people, such as those with cancer, are infected longer because their bodies cannot fight the virus as quickly. The theory is that this gives the virus an environment to stay and develop mutations, before spreading to another person.
But Turville said that in countries where Covid-19 is out of control, the large number of infected people makes it more likely that there will be a rare event that leads to an “explosion in changes in the virus that you would not otherwise see. “. .
“It can come down to the fact that in the really affected areas, there are more opportunities for a rare virological event,” he said. Turville and other researchers hope to learn more about these variants in the work they are doing in the containment laboratory of the Kirby Institute, a high-security laboratory that receives samples of the virus from international travelers in Australia’s hotel quarantine system.
Turville then uses these swabs to grow the virus. Every time someone enters the lab, they don multiple layers of clothing covered by full personal protective equipment that includes breathing masks, rubber boots, and overalls on top. Turville goes through a series of negative pressure chambers before entering the containment lab, where it can only work for short periods of time to avoid overheating.
“We get swabs from the quarantine of all the new virus flavors that you see there, then we grow them and we need to see how they behave in the lab. That helps us know if someone who had an antibody response after being infected with a different variant in March will show a response similar to one of the newer variants. “
Turville said the good news is that while some of the new variants can blunt an antibody response or a vaccine response, none to date have been able to completely evade the immune response.
“To date we have yet to see a single mutant virus with complete immune evasion that would render a vaccine useless,” he said.
