Mu variant: what is known about coronavirus strain prevalent in Colombia | Coronavirus

Just over a week ago, a coronavirus variant first identified in January in Colombia has entered the list of mutations in Sars-CoV-2 under monitoring by the World Health Organization (WHO).

THE variant Mu (or B.1.621) came to be considered a “variant of interest” by the WHO, for having “a constellation of mutations that indicate potential properties of escape from immunity”, that is, the protection of vaccines – which still needs to be confirmed by further studies, according to the bulletin of the organization released on August 31st.

  • Minas Gerais has 5 confirmed cases of the mu variant of the new coronavirus
  • WHO monitors new coronavirus variant detected in Colombia

Mu is, for the time being, a “variant of interest” being monitored by the WHO – the variants Alpha, Beta, Gamma (the one identified in Brazil) and Delta are considered “variants of concern”.

“Since it was identified in Colombia in January 2021, there have been some sporadic records of Mu variant cases and some larger outbreaks have been reported in other countries in South America and Europe,” says the WHO bulletin.

Coronavirus 'Mu' variant advances in Colombia and Ecuador

Coronavirus ‘Mu’ variant advances in Colombia and Ecuador

For now, the intergovernmental agency continues, the prevalence of Mu is less than 0.1% among sequenced cases of coronavirus worldwide.

But locally, its prevalence has “constantly increased” in Colombia and Ecuador, where it accounts for – respectively – 39% and 13% of cases sequenced. These data, however, should be read with caution, says the WHO, since most countries in the world have a low capacity to monitor the genetic sequencing of Covid-19 variants.

It is currently estimated that Mu circulates in more than 40 countries, including Brazil – there are already confirmed case reports around here.

But, according to the open platform Gisaid, which compiles viral genomic data, Mu represents 0% of cases sequenced in Brazil. The platform has calculated that, so far, there are ten identified cases of Mu out of a total of nearly 35,000 sequenced, that is, cases in which the virus had its genomic analysis performed.

In Mexico, Mu represents 1% of the cases sequenced. In the US, 0%, but in absolute numbers, more than 1,700 cases of Mu sequence were detected.

In Colombia, health authorities have told the local press that Mu is already the predominant variant in circulation in the country, which so far has less than a third of its population vaccinated against the virus.

The third wave of Covid-19 in the South American country, between April and June, has been attributed to this variant.

During this period, when Colombia registered around 700 deaths a day, nearly two-thirds of genetic tests carried out on fatal victims indicated the presence of the Mu variant, Marcela Mercado, research director at the Institute, told local radio on Sept. 2 National Health.

Delta still focuses concerns

The Colombian institute pointed out that the Mu variant has been shown to have a great transmission capacity.

It is important to highlight that the emergence of variants is expected within the advance cycle of a virus during a pandemic like the current one, especially in places where the circulation of this virus is still high. Most mutations have little or no effect on the virus’s properties.

But, in this process, some more dangerous variants emerge – and so far Delta is the one that raises the most concern in the world, having demonstrated a great transmission capacity and having already been identified in about 170 countries.

In the State of Rio de Janeiro, for example, Delta is considered the predominant variant since mid-August.

“When a virus establishes itself, there starts to be a competition between the various strains, or types of virus. This favors the more transmissible types that generate more cases, as it has been with Delta in all the places it has passed through in the world. “, explains to BBC News Brasil the doctor in microbiology and scientific popularizer Átila Iamarino.

What makes Delta more problematic, he says, is that people infected with this variant can have large amounts of virus in the upper airways (such as the nose, mouth, and larynx) sooner than they would with the original version of the coronavirus, even if asymptomatic. With more virus in the body, that person can transmit it more easily and have their immune system tested harder. Therefore, Iamarino details, “Delta infects at least twice as much as the traditional coronavirus”.

“Any other variant needs to compete with this to be able to predominate, and none of them has done that so far. (…) Regardless of whether the variant comes from the side (as in the case of Mu in Colombia) or from India, it’s a matter of time for (a variant as transmissible as Delta) to predominate, as we saw it happen.”

What is alarming is the fact that Delta has advanced even in countries that already have high vaccination coverage. This does not mean, however, that this vaccine coverage has no effect, quite the contrary: the more people vaccinated with two doses (or with a single dose vaccine), the less chance that variants will emerge and find ground to proliferate.

“Although people with up to two doses can contract and transmit Delta, vaccines still stop it very well,” continues Átila Iamarino. “She’s clearly worrying, but we managed to stop her.”

What stands out in the Mu variant

What about the Mu variant? In an article on the academic platform “The Conversation”, the professor of biochemistry at the University of Trinity College, Ireland, Luke O’Neill, summarized what makes this variant have entered the WHO radar.

O’Neill explained that, according to studies still in the pre-print phase (and therefore still needing scrutiny by the scientific community), Mu has a mutation called P681H, similar to that seen in the British variant Alpha and potentially making it more transmissible . “(But) we can’t be sure of the effects of P681H on virus behavior so far,” wrote O’Neill.

Other Mu mutations are also associated with an increased ability to evade antibodies created against the coronavirus, the researcher continued. In this case, the evidence appears to be more robust. “These mutations also occur in the Beta variant, and it is possible that the Mu behaves like the Beta, against which some vaccines are less efficient”, he detailed.

O’Neill reinforced the WHO conclusion that the Mu variant still needs further study, so that we can better understand its behavior and therefore its danger. “The epidemiology of Mu in South America, particularly with Delta’s co-circulation, will be monitored,” wrote WHO in its newsletter.

As of 29 August, the WHO said, there were more than 4,500 confirmed genomic analyzes of the Mu variant around the world, identified in the previous four weeks and counted by the Gisaid platform.

For Attila Iamarino, it is important to continue to monitor variants, such as Mu, even if so far they do not seem as threatening as Delta. It is only with this type of monitoring that we will know, for example, if any variant other than Delta will be able to advance in places with high vaccination rates – something that would be a “very big warning sign”, says the microbiologist.

Once the greatest advance in vaccination in the world can better stop Delta’s advance, “it may be that, up ahead, other variants that are not so transmissible, but that escape vaccination, will be able to predominate. But this is not the case until now. here, where Delta predominates both in places that vaccinated a lot and in places that vaccinated little,” says Iamarino.