Japan’s Ministry of Health, Labor and Welfare announced its first two cases of COVID-19’s Mu variant in quarantine at two domestic airports in June and July this year.
The variants were detected in a woman in her 40s who arrived on June 26 from the United Arab Emirates. Another woman in her 50s who arrived in Japan on July 5 from the U.K. also had the Mu variant, it said. Both women were asymptomatic.
The World Health Organization (WHO) classified Mu variant, or B.1.621 as a “variant of interest,” (VOI) on August 30. The Mu variant has a constellation of mutations that indicate potential properties of immune escape. How transmissible it is or whether it can evade vaccine protections is still not known.
The Mu strain was discovered in Colombia in January this year and has been reported in South America and Europe. Although the global prevalence of the Mu variant among sequenced cases has declined and is currently below 0.1%, the prevalence in Colombia (39%) and Ecuador (13%) has consistently increased, WHO notes.