COVID-19: New 'Mu variant' from Colombia could be vaccine resistant - WHO

A number of mutations suggest that the Mu variant could resist immune defenses and possibly even have a faster transmission than other variants.

This undated transmission electron microscope image shows SARS-CoV-2, also known as novel coronavirus, the virus that causes COVID-19, isolated from a patient in the U.S. Virus particles are shown emerging from the surface of cells cultured in the lab. The spikes on the outer edge of the virus parti (photo credit: NIAID-RML/FILE PHOTO/HANDOUT VIA REUTERS)
This undated transmission electron microscope image shows SARS-CoV-2, also known as novel coronavirus, the virus that causes COVID-19, isolated from a patient in the U.S. Virus particles are shown emerging from the surface of cells cultured in the lab. The spikes on the outer edge of the virus parti
(photo credit: NIAID-RML/FILE PHOTO/HANDOUT VIA REUTERS)

The World Health Organization (WHO) is closely monitoring the emergence of a new variant of the novel coronavirus, the Mu variant, which has already been spreading through South America and has shown signs of possible vaccine resistance.

First identified in January 2021 in Colombia, the Mu variant has seen sporadic cases emerge throughout South America and Europe. Globally, the variant accounts for less than 0.1% of all cases worldwide. However, the WHO has noted that it has become considerably more prevalent in Colombia and Ecuador, where it accounts for approximately 39% and 13% of respective cases.

Further research is needed to accurately verify if this new variant, also known by the designations VUI-21JUL-01 and B.1.621, could be resistant to vaccines. The WHO is still monitoring it as a Variant Of Interest, as there are several mutations, two of which were designated E484K and K417N, suggesting it could resist immune defenses in a similar manner to the Beta variant found in South Africa.

Another mutation found, dubbed P681H, has also caused some concern, as this could make the variant more infectious, similar to the Alpha variant found in the UK, according to The Guardian. However, it isn’t clear if this is in fact more contagious than other variants, with an August report by Public Health England noting, “At present, there is no evidence that VUI-21JUL-01 is outcompeting the Delta variant and it appears unlikely that it is more transmissible.”

The Mu variant has been detected in some 40 countries so far, including the UK, US, Hong Kong and in Europe, and could spread further.

On Thursday, Japan’s Health Ministry confirmed that two Mu variant cases were detected in the country in June and July during airport screenings, the former having been an arrival from the UAE and the latter having arrived from the UK, though both were asymptomatic, the Japan Times reported. According to The Guardian, some 32 people in the UK have been diagnosed with the Mu variant, with the infection patterns indicating that people entering the country had brought it with them.

 COVID-19 cell (credit: BAR ILAN UNIVERSITY)
COVID-19 cell (credit: BAR ILAN UNIVERSITY)

But Mu isn’t the only new variant causing concern. Recently, scientists found another variant in South Africa and a number of other countries, designated C.1.2, with concerns that it could be more infectious and evade vaccines, according to a new preprint study by South Africa’s National Institute for Communicable Diseases and the KwaZulu-Natal Research Innovation and Sequencing Platform, which is awaiting peer review.

Scientists first detected C.1.2 in May 2021, finding that it was descended from C.1, which scientists found surprising since C.1 had last been detected in January. The new variant has “mutated substantially” compared to C.1 and is more mutations away from the original virus detected in Wuhan than nearly any other variant.

While first detected in South Africa, C.1.2 has since been found in England, China, the Democratic Republic of the Congo, Mauritius, New Zealand, Portugal and Switzerland.

The South African study comes as a doctor in Turkey reported indications that a new coronavirus variant had been detected in the country, with tests detecting mutations that weren’t found in the current variants named by the WHO.


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The coronavirus pandemic originated in Wuhan, China, and has since spread worldwide. Over the past two years, the disease has infected hundreds of millions of people. The global death toll is estimated at around 4.5 million.

Tzvi Joffre contributed to this report.