SARS-CoV-2 Mu variant

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The Mu variant, also known as lineage B.1.621 or VUI-21JUL-1, is one of the variants of SARS-CoV-2, the virus that causes COVID-19. It was first detected in Colombia in January 2021 and was designated by the WHO as a variant of interest on August 30, 2021.^[1] On 16 March 2022, the WHO has de-escalated the Mu variant and its subvariants to "previously circulating variants of concern".^[2][3]

The WHO said the variant has mutations that indicate a risk of resistance to the current vaccines and stressed that further studies were needed to better understand it.^[4][5] Outbreaks of the Mu variant were reported in South America and Europe.^[6] The B.1.621 lineage has a sublineage, labeled B.1.621.1 under the PANGO nomenclature, which has already been detected in more than 20 countries worldwide.^[7]

Under the simplified naming scheme proposed by the World Health Organization, B.1.621 was labeled "Mu variant", and was considered a variant of interest (VOI), but not a variant of concern.^[1]