Cases of Mu COVID Variant That May Evade Vaccines Found in These States

The Mu COVID-19 variant, which some scientists worry may evade vaccines, has been detected in the vast majority of states in the United States, although it accounts for fewer than 1 percent of total cases in the U.S.

The World Health Organization (WHO) labeled the Mu strain a variant of interest on Monday, the fifth variant to earn the designation. Officials' concerns about the variant stem from its mutations, which indicate it could have the potential to evade vaccines, and, while cases are low, the WHO noted in a report that they're consistently increasing in Colombia, where it originated, and Ecuador.

All but three states in the U.S.—Nebraska, Vermont and South Dakota—have had reported cases of the Mu variant, according to, an open source database from Scripps Research. It has been most prevalent in Alaska, where it accounted for about 4 percent of nearly 4,000 samples.

Fifteen states—Maine, New Hampshire, West Virginia, South Carolina, Tennessee, Kentucky, Alabama, Mississippi, Louisiana, Arkansas, Missouri, Iowa, North Dakota, Montana and Oklahoma—have had 10 or fewer cases.

Twenty-four states have had between 11 and 50 cases and four—New York, New Jersey, Texas and Washington—have had up to 100 cases. Only one state, Florida, has had between 100 and 200 cases, and California has had the most at 289 cases, according to

mu variant detected us states
The Mu variant, which is now classified as a variant of concern, has been found in the majority of U.S. states. Above, people wear face masks while walking on Fifth Avenue on April 10, 2021, in New York City. Noam galai/Getty Images

Since its identification in January, the WHO noted there have been "a few sporadic reports" of cases of the Mu variant. While the properties of its mutations lend itself to the hypothesis that the variant could infect people who have natural immunity to COVID-19 or have been vaccinated against the virus, more research is needed to confirm if that's the case. It's also possible monoclonal antibody treatments, which have yielded promising results in patients, might not work as well against the Mu strain.

Mutations in SARS-CoV-2 have been expected to occur, as it's natural for a virus to evolve over time. Currently, the WHO is tracking four variants of concern—Alpha, Beta, Gamma and Delta—which are all either more transmissible, cause more serious disease or decrease the effectiveness of public health measures, including vaccines and therapeutics.

Delta, which was classified as a variant of concern in May, is the dominant strain in the United States and is fueling large-scale outbreaks among unvaccinated individuals. Along with the four variants of concern, WHO is monitoring five variants of interest—Eta, Iota, Kappa, Lambda and Mu—because they all have genetic changes that could make them more transmissible or dangerous to humans and have been found to cause multiple clusters in multiple countries.

Although vaccines are never 100 percent effective, the inoculations that have been approved for use have shown to be a great weapon against contracting COVID-19 and keeping people from getting seriously ill if they do test positive. However, health officials are concerned that if the virus continues to circulate unmitigated, a variant will emerge that resists vaccines.

If a variant manages to render vaccines ineffective, it would require scientists to create a new vaccine and for countries to revaccinate their populations. A tall order given the extraordinary effort that it has taken to reach the current level of vaccinations, it would extend the pandemic, elongating the human and economic toll of the crisis.