The Mu variant of the coronavirus is something to monitor – as it appears to partially evade immunity from authorized COVID-19 vaccines – but Delta’s continued dominance means “Mu is not an immediate threat,” says NIAID Director Dr. Anthony Fauci.
The World Health Organization (WHO) recently labeled the coronavirus variant known as Mu (B.1.621 and first discovered in Colombia) a variant of interest (VOI). A VOI is one step below what is known as a variant of concern (VOC), such as the Delta variant.
As for the concern over the Mu variant? According to Axios, Anne Rimoin, an epidemiologist and director of the UCLA Center for Global and Immigrant Health says Mu may “indicate potential properties of immune escape, as it has some of these hallmarks of being able to get around that existing vaccine protection, but it doesn’t mean that’s what we’re seeing play out in real life.”
In reality, only about 0.5 percent of new cases are showing as Mu, Dr. Fauci says, with 99.3 percent testing as Delta, which has such an “extraordinary ability” to transmit that it won’t likely lose its global dominance in the immediate future.
The main drivers behind new coronavirus variants
For any organism, including a virus, copying its genetic code is the essence of reproduction – yet this is not always perfect. Coronaviruses use RNA for their genetic information and copying RNA is more error-prone than using DNA.
Research has shown that when the coronavirus replicates, around 3.0 percent of the new virus copies have a random error, called a mutation. However, the number of mutated viruses is dwarfed by the much larger number of viruses that are the same as the strain that started the infection.
And while most mutations are harmless, they don’t change how the virus works. But there are a very small fraction of mutations that make the virus more contagious, and these mutations need a bit of luck in becoming a new variant.
To give rise to a new variant, it must successfully jump to a new person and replicate many copies. The small odds of a mutant being transmitted is called the “population bottleneck.”
Getting past the so-called bottleneck is difficult, if a fast-spreading strain is able to cause a large number of COVID-19 cases somewhere, it will start to out-compete less contagious strains and generate a new variant, just like the Delta strain did.
With more than a million new infections occurring every day and billions of people still unvaccinated, susceptible hosts are rarely in short supply. So, natural selection will favor mutations that can exploit all these unvaccinated people and make the coronavirus more transmissible.
And that is the secret to why the pandemic is still going full blast around the world today. This also means that the best way to put a halt to the evolution of the coronavirus is to reduce the number of infections.
The MU variant versus the Delta variant
The Mu variant shares mutations with other variants, most notably the Beta (B.1.351) variant first identified in South Africa. These include the E484K and K417N mutations, which researchers have linked to immune escape.
Additionally, Mu has the P681H mutation seen in the Alpha (B.1.1.7) variant, which is associated with increased transmissibility, reports The Scientist.
According to Outbreak.info, Mu has been detected in at least 46 countries as of September 7, including the United States, where Delta continues to dominate but more than 2,100 cases of Mu have been reported.
The New York Times reports that Dr. Fauci says US officials are keeping a close eye on the Mu variant. “We take everything like that seriously, but we don’t consider it an immediate threat right now.”
Scientists at the Medical University of South Carolina are closely studying the coronavirus mutations. Their findings are shared with researchers around the world.
Dr. Julie Hirschhorn, Director of MUSC’s Molecular Pathology Laboratory, says that “99 percent of the samples we sequenced throughout August were all Delta and it was over 300 samples.
Additionally, she says the more cases we have, the more opportunity the virus has to mutate. Hirschhorn says her team is discovering more versions of Delta each week.
“Last week I think there were 12 and this week there were 31,” she explained, according to News 19. “The virus loves to mutate.” MUSC scientists are also looking at how the virus changes with new mutations and how these small differences can make a big impact on the body.
MUSC’s findings on the Delta mutations are posted on an international database, meaning scientists across the globe can use the information to track variants in their own communities and prepare for what could come in the future.
It all comes down to vaccinations
Dr. Hirschhorn, like Dr. Fauci and other epidemiologists around the world, agrees that the only way to stop the spread of variants and stop the pandemic in its tracks is to get people vaccinated.
For now, it is unlikely that vaccine-induced immunity will be the major player in variant emergence because there are lots of new infections in the unvaccinated occurring on a daily basis. It’s simply a numbers game.