The Mu COVID-19 variant has been attracting more and more attention in recent weeks and has recently been designated as a “variant of interest” by the World Health Organization (WHO). But is Mu more dangerous than the Delta variant that fuels the latest wave of infections in the United States?
The Delta variant has spread to more than 170 countries around the world since it was first identified in India in October 2020, becoming dominant in many regions.
In the United States, for example, Delta is now fully dominant, accounting for more than 99% of new cases of COVID-19, according to data from the Centers for Disease Control and Prevention (CDC).
According to the CDC, the Delta variant causes more infections and spreads faster than previous forms of SARS-CoV-2, the virus that causes COVID-19.
Studies show that Delta is highly contagious, perhaps more than twice as contagious as previous variants.
There is also some evidence to suggest that Delta could cause more serious diseases than the previous variants in unvaccinated people.
Some research has shown that individuals infected with Delta, which has been categorized as a “variant of concern” by the CDC, appear to have viral loads 1,000 times higher than those observed with previous variants.
Although COVID-19 vaccines are effective in reducing Delta infections as well as serious diseases, advanced cases can still occur. People completely vaccinated with advanced infections can still spread the virus to others, even though they appear to be infectious for a shorter time.
Delta has multiple mutations in the tip protein of the virus. This particular set of mutations make the variant much more effective at binding and entering human cells, which is why it is so contagious.
Much less is known about the Mu variant, which the WHO added to its list of “variants of interest” (VOI) on 30 August.
The variant, which was first identified in Colombia in January 2021, has now been confirmed in more than 40 countries around the world and in 50 US states.
The WHO designated Mu as VOI due to major outbreaks in South American countries such as Colombia and Ecuador, as well as parts of Europe.
But in the United States, Mu accounted for only about 0.1 percent of new infections in the week ending Sept. 11, according to the CDC. And the proportion of new cases caused by the new variant has been declining since July, as Delta has become more dominant. The CDC has not yet included Mu as YOU.
The Mu variant has several mutations in the ear protein, with initial research indicating that it may be more resistant to vaccines or natural immunity than previous variants (although its extent is still unclear).
But WHO officials have said the Delta variant is a much more urgent concern because of its highly contagious nature.
Maria Van Kerkhove, technical manager of the COVID-19 agency, said during a virtual press conference last Tuesday: “The Delta variant for me is the one that worries me the most because of the increased transmissibility.”
“In some countries, the proportion of cases with the Mu variant is increasing,” Van Kerkhove said. “But in other countries, the proportion of Mu is declining. Where Delta is, Delta is taking over quickly.”
Dr Mike Ryan, head of the WHO health emergency program, told the press conference that any new variant must compete with the “best in class”, which is currently Delta. This variant tends to “outperform” other variants, he said, even if they are better at circumventing the protection offered by vaccines or natural immunity.
In early September, the White House chief medical adviser, Dr. Anthony Fauci said U.S. health authorities were closely monitoring Mu while minimizing the threat of the variant.
“We look at it, we take it seriously, but now we don’t consider it an immediate threat,” Fauci said at a Sept. 2 press conference.
John P. Moore, a professor of microbiology and immunology at Weill Cornell Medical College, said this earlier Newsweek that while Mu has some “worrying mutations,” it is not spreading widely in the United States.
“I’ve seen very few studies on its properties because it hasn’t been studied extensively yet. The most important thing is that it just doesn’t spread much.”
The fact that Mu is not spreading as fast as Delta could mean the new variant will gradually disappear, according to Moore.
“One of the things we’ve learned with Delta is that it raised less transmissible variants,” Moore said. “They are the most transmissible variants that dominate. And everything else becomes less and less of a problem. Unless Mu has unique transmissibility properties, and that would be surprising because it hasn’t been seen so far. It’s the survival of the fittest since the perspective of the virus. “
And even if Mu is more resistant to vaccines than other strains, experts say the shots currently available will still be effective in protecting against serious disease.
Jesse Erasmus, PhD, director of virology at HDT Bio and assistant professor at the University of Washington School of Medicine in Seattle, told WebMD: “A prepress study (not yet peer-reviewed) came out on 7 September and shows that Mu is a little more resistant to the vaccine than the beta variant. “
“When we talk about vaccine leakage, we need to be very careful to specify that it is about escaping infection, not serious disease. Even against the most resistant vaccine variant that exists, vaccines still protect against diseases “.
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