In September, news broke that a new mutation in the coronavirus – the mu variant, officially known as B.1.621 – could potentially evade vaccine-induced immunity.
“This variant has a constellation of mutations that suggest it would escape certain antibodies, not only monoclonal antibodies, but antibodies induced by vaccines and convalescent sera,” said COVID-19 adviser to President Joe Biden, Dr Anthony Fauci, to reporters in September. “But there isn’t a lot of clinical data to suggest that. It’s mostly in vitro laboratory data.”
At the time, the idea of ​​a vaccine-resistant variant sent a shock wave of fear across the world. The dreaded delta variant was already known to be more resistant to vaccines than the original SARS-CoV-2 virus. Mu, which was first discovered in Colombia, could it be worse than Delta? Indeed, mu appeared to have specific mutations that have been associated with resistance to immunity, as well as a mutation known as P681H that has been linked to accelerated transmission.
Now, nearly a month later – long after the World Health Organization dubbed the mu variant of “interest” that needed to be watched – data from the epidemic.info shows that the mu variant has not been detected in the United States, or anywhere in the world, since September 21, 2021.
Does that mean mu is no longer a threat? The short answer is: probably. But Joseph Fauver, an associate researcher at the Yale School of Public Health, wouldn’t go so far as to say he has been “eradicated,” as some news outlets have reported either.
“To say that it has been ‘eradicated’ would imply that we humans have done everything possible to make it happen… but as far as mu or B.1.621 are more present, yes, I would totally buy that.” , Fauver said.
Fauver clarified: “What really happened was that he was effectively passed by delta.”
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A similar trend was seen with the alpha variant, or B.1.1.7, which was first found in the UK. According to Epidemic.info, a multi-agency coronavirus public health database that collects genomic data from the GISAID Initiative, B.1.1.7 was last detected in the United States on September 17. 2021. It was last detected worldwide in September. 21, 2021.
As Fauver explained, these dates are derived from the last known genetic detection of each variant in random patient samples. Since not all COVID-19 cases are sampled and DNA tested, there is no way to know with absolute certainty if these variants are still circulating, especially when positive case rates for COVID-19 are. as high as in the United States.
But over the weeks, the delta variant continues to be the dominant variety in the world.
Delta’s dominance over other varieties can be a blessing in disguise. This is because delta spreads 50% faster than alpha and is 50% more contagious than previous variants. Yet mu certainly had its own set of disturbing mutations.
“Mu contains a series of very disturbing mutations,†Fauver said. “The mutations that have been found in many of the other variants of concern, particularly in the Spike gene and the receptor binding domain, also by various studies, appear to be slightly more immuno-evasive than some of the other variants of concern.”
Fauver added: “If it hadn’t been for delta it might have been of much more concern and could have reached much higher frequencies.”
If so, why did the Delta variant win?
“A million dollar question,†Fauver said. “I can say with confidence that delta is more transmissible, but exactly why, I think the jury is still out and there is still more science to be done.” Fauver speculated that it might have to do with something going on at the molecular level.
If the variants that were the first part of the pandemic essentially die and the delta is the dominant in the world, does that mean that the delta is the variant that we can expect to stay in the long term? Not yet. This is because RNA viruses like SARS-CoV-2 are always mutating. Although viruses are technically not alive, it is their nature to mutate and evolve as they infect host cells and replicate.
In fact, the delta variant has already mutated, but not in a significant way for humans. In general, the rate at which mutations occur depends on the virus.
“Viruses replicate, survive and pass their genes on to the next generation simply by making more copies of themselves,” said Sasan Amini, founder and CEO of Clear Labs, a privately-held genomics company. “This process of replication is not a perfect process, which means that while you go through the process of replication, errors will be introduced. But these errors are in fact fixed and the result of this ends up creating almost identical copies. to each other. “
Many mutations are removed during the process of natural selection, Amini said, but sometimes mutants gain a competitive advantage, like delta.
“These mutants end up replicating faster, are more infectious, and eventually become the most prevalent part of the population,” Amini said. “And that’s pretty much what happened.”
Amini said that some of the delta mutations are similar to mu, but not all. All this to say that it is possible that delta could mutate into something different.
“Not everything that is defined as delta today will be pretty much the only SARS-CoV-2 you see in the future,†Amini said. “And as a result, that actually means that it is very essential for any government entity, public health entity, the entire public health response, to monitor and sequence the emerging and existing versions of SARS-CoV-2.”
Does that mean an even worse iteration of delta awaits you? Fauver said he was not in the “prediction business,” but said many mutations seen in the worrisome variants are shared. They have, he says, the same “repertoire”.
“Is there a new set of mutations, waiting to be found, to make the virus worse? I have no idea,” he said. “The delta is really transmissible, it’s a very bad virus, and I hope it doesn’t get much worse than that.”
