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The Mu coronavirus variant has been recorded in 49 US states, with Florida and California reporting the highest numbers of Mu infections. California has recorded 384 Mu variant cases, with 167 cases contained in Los Angeles County area. Until recently, Alaska had the highest number of Mu cases, with 146 people testing positive for the variant. With its relatively small population, of 730,000 people, Mu made up four per cent of the state’s sample size.

Nebraska is the only state in the United States to have not detected a case of the Mu variant of COVID-19, which may render vaccines less effective.

Since being first identified in Colombia in January, the Mu variant has spread to 41 countries, including the United States. Mu is not an “immediate threat“, said Dr Anthony Fauci, in a news conference. But scientists will be “keeping a very close eye on it”.

“This variant has a constellation of mutations that suggests that it would evade certain antibodies, not only monoclonal antibodies, but vaccine- and convalescent serum-induced antibodies,” he said.

At least one case of the Mu variant has been detected in the District of Columbia and every state in the U.S. aside from Nebraska, according to, a website that provides open source data on COVID-19 variants.

LA County Public Health issued a statement explaining more work is needed to tell what we are dealing with: “More studies are needed to determine whether Mu variant is more contagious, more deadly or more resistant to vaccine and treatments than other Covid-19 strains,” it said.

Maine, Connecticut and Florida round out the list of states with the highest prevalence of Mu cases. Florida’s had the second-highest number of samples, at 384 of the 60,475 samples that were sequenced being of the Mu variant.

The World Health Organization labeled Mu a variant of interest on August 30 because its characteristics could make it more transmissible or resistant to vaccines. However, the Centers for Disease Control and Prevention (CDC) has yet to make the same classification.