What We Know About Mu, the WHO’s Latest Variant of Interest

The SARS-CoV-2 variant was first detected in January, but its rising prevalence and potential resistance to vaccines has garnered it special attention from the World Health Organization.

Written byChristie Wilcox, PhD
| 2 min read
tube of blood labeled positive for COVID-19 Mu variant

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Tthe Mu variant (also known as B.1.621) is the latest form of SARS-CoV-2 to be designated a “Variant of Interest” by the World Health Organization. The agency announced the designation had been made in last week’s epidemiological update, citing an uptick in Mu infections in Ecuador and Colombia, where the variant was first identified in January. In Colombia, it underlies nearly 40 percent of cases, according to WHO data.

According to Public Health England, the variant shares mutations with other variants, most notably the Beta (B.1.351) variant first identified in South Africa. These include the E484K and K417N mutations, which researchers have linked to immune escape. K417N is also seen in the “Delta plus” variant. Additionally, Mu has the P681H mutation seen in the Alpha (B.1.1.7) variant, which is associated with increased transmissibility.

Detailed studies of the Mu variant’s characteristics have yet to be conducted, but ...

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