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WHO Watches Mu

The World Health Organization (WHO) is tracking a SARS-CoV-2 variant known as the Mu variant, or B.1.621, The Guardian reports. As of August 30th, the variant is part of a WHO variant watchlist.

The WHO has designated four SARS-CoV-2 variants — Alpha, Beta, Gamma, and Delta — as variants of concern. The Mu variant joins the organization's "variants of interest" list, which encompasses forms of SARS-CoV-2 implicated in COVID-19 clusters or community transmission that are becoming more prevalent or risky, and contain genetic mutations "known to affect virus characteristics such as transmissibility, disease severity, immune escape, diagnostic, or therapeutic escape," a WHO website explains.

The latest variant of interest contains mutations suspected of helping the virus move more quickly between individuals, while dodging some of the immune features conferred by vaccination or prior infection, The Guardian's Ian Sample explains.

"Scientists and public health officials are particularly eager to know whether the Mu variant is more transmissible, or causes more serious disease, than the Delta variant that is dominant in much of the world," Sample writes, noting that Public Health England has included the Mu variant in its "variants under investigation" list since July.

The variant was initially flagged in Colombia early this year and has since been identified in dozens of countries.

"Mu was first identified in Colombia in January, and is not responsible for 39 [percent] of cases in that country, the WHO says. Global prevalence of the variant is low, and falling, the agency says, but in recent weeks it has grown sharply in both Colombia and in Ecuador, where it now represents 13 [percent] of sequenced cases," Barron's reports.