Covid 19 coronavirus: WHO designates ‘Mu’ as new Covid variant of interest

The World Health Organization is monitoring a new coronavirus variant known as “Mu”, amid concerns that it has mutations which suggest it is more resistant to vaccines.

In a weekly pandemic bulletin the UN agency said Mu – known scientifically as B.1.621 – has now been designated as a “variant of interest”, a classification used to target research and highlight potentially worrying new strains.

“The Mu variant has a constellation of mutations that indicate potential properties of immune escape,” the WHO report said.

It added that preliminary data suggests Mu may be able to evade antibodies generated from both prior infection and coronavirus vaccines at levels “similar to that seen for the Beta variant”, though this finding needs to be confirmed in further studies.

Beta is one of four strains categorised as a “variant of concern” by the WHO. Earlier this year South Africa – which first detected Beta – stopped using the AstraZeneca shot after a small study suggested the jab offers only limited protection against mild illness caused by the strain. Subsequent research, though, suggests Covid vaccines still prevent severe disease and death.

The Mu variant was first detected in January in Colombia, where prevalence has “consistently increased”; the WHO said it comprises 39 per cent of sequenced infections. Rates are also rising in neighbouring Ecuador, where Mu is responsible for 13 per cent of cases.

But globally, the variant’s prevalence has actually declined and it makes up less than 0.1 per cent of sequenced infections. So far just over 4,500 cases have been uploaded to Gisaid, a scientific database that is tracking variants globally, from 39 different countries.

However, the WHO warned that “reported prevalence should be interpreted with due consideration of sequencing capacities and timeliness of sharing of sequences”, which vary widely across the globe.

Dr Julian Tang, clinical virologist at the University of Leicester, said Mu shares three mutations (called E484K, N501Y, and P681H) common to other variants of concern, including Alpha and Beta. “We know that these [spike] protein mutations give rise to some degree of vaccine escape and increased transmissibility,” he told The Telegraph.

“[Mu] also has mutations in other parts of the virus genome that may make it behave slightly differently from the other variants – but lab and real-world studies will be needed to fully characterise the impact of this.”

It follows the announcement on Tuesday that another new Covid variant was detected at the New Zealand border. It is not the Mu variant but is known as C. 1.2.

A new preprint study by South Africa’s National Institute for Communicable Diseases warns the new variant has “mutated substantially” and is more mutations away from the original virus detected in Wuhan than any other variant previously detected.

The new variant first emerged in South Africa but has also been detected here, as well as England, China, the Democratic Republic of the Congo, Mauritius, Portugal and Switzerland.

A Ministry of Health spokesperson confirmed to the Herald that a case of the new variant was identified at the border in Auckland in late June 2021.

'A stark reminder this isn't over'

The new variant comes amid mounting concerns that low global vaccination rates and high transmission rates poses a perfect window for the emergence of new variants.

All viruses mutate as they reproduce, with most changes of little consequence. But occasionally a mutation emerges which affects how infectious a variant is, the severity of the disease it causes, or its ability to evade vaccines and treatments.

Prof Danny Altmann, an immunology expert at Imperial College London, told The Telegraph that the emergence of new variants is a stark reminder that the pandemic is not over.

“At the moment, it looks like there’s genuine cause for concern in USA, Central America, South America, but as we saw with Delta, a potent variant can traverse the globe in the blink of an eye,” he said.

“Mu looks potentially good at immune evasion. For my taste, it’s a stark reminder that this isn’t by any means over: on a planet of 4.4 million plus new infections per week, there are new variants popping up all the time, and little reason to feel complacent,” Prof Altmann added.

Others are less concerned. “A variant a day keeps the doomers in play,” Prof Francois Balloux, director of the Genetics Institute at University College London, wrote on Twitter.

To date, the UN agency has classified four variants of concern – Alpha, Beta, Delta and Gamma – alongside five variants of interest, including Mu.

In an interview with The Telegraph last month Maria Van Kerkhove, technical Covid-19 lead at the WHO, said new coronavirus variants could be named after star constellations once the 24 letters of the Greek alphabet are exhausted – an eventuality she considers likely.

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