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The Mu variant of SARS-CoV-2 has spread to 49 states, at least 46 countries

Nebraska is the only state to have not recorded a case with the Mu variant.

September 7, 2021 4:10pm

Updated: September 7, 2021 5:58pm

The World Health Organization (WHO) has designated the Mu variant of SARS-CoV-2 as a "Variant of Interest," spreading to 49 U.S. states and 46 countries.

The Mu variant was first identified in Colombia in January, and makes up nearly 40% of cases there, according to the WHO.

There are over 2,100 cases of Mu in the U.S., and it has spread to 49 states, with Nebraska being the only one that hasn't recorded it, according to, which is a data aggregation site that is maintained by three Scripps Research labs. Mu accounts for four percent of cases in Alaska, at 147. California has the highest amount of Mu cases in the U.S., reporting 399, with Florida following at 305 cases, and New York at 203.

Some mutations found in Mu are consistent with the Alpha, Beta, and Delta variants, including increased transmissibility and linkage to immune escape, according to Public Health England.

While detailed studies of the variant characteristics of Mu have not been conducted yet, preliminary data given to the WHO's Virus Evolution Working Group shows that it exhibits an escape of immune protection from vaccines like the Beta variant, UN News reported.

Paúl Cárdenas, an infectious disease researcher with Universidad San Francisco de Quito in Ecuador, told The Washington Post that based on his studies of Mu, it is "more transmissible" than the original SARS-CoV-2, and has "been able to outcompete gamma and alpha in most parts of Ecuador and Colombia."

Pfizer spokesperson Kit Longley remained optimistic, telling The Post in an email that the company is studying Mu and plans on sharing its data with a peer-reviewed journal soon. "To date, we are encouraged by both the real-world data and laboratory studies of the vaccine and see no evidence that the virus or circulating variants of concern regularly escape protection," she said.

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