On the first day of September, Japan reported the arrival of the Mu COVID-19 strain in its country.  

The Mu variant, also known as B.1.621, was categorized into the World Health Organization (WHO)’s list of “variants of interest” on Aug. 30.

Japan’s health ministry announced there were two patients infected with the variant. Both were women and asymptomatic, according to Japan Times.

One patient, who was in her 40s, arrived in the country on June 26 from the United Arab Emirates. The other one was in her 60s, came to Japan on July 5 from the UK. 

While neither of them displayed symptoms upon arrival, no information about their vaccination state had been disclosed.

According to Japan Times, every traveler to the country must undergo PCR tests and wait for their results. If the individual tests positive, they must be quarantined in a designated facility or hospitalized, depending on their symptoms. 

In case of negative results, 14-days quarantine is still compulsory, but the traveler can stay at home or at a certified facility, which would be determined on where they arrived from.

The Japan health ministry said it was keeping a close eye on the manifestation of the Mu variant in other countries and taking measures to contain the spread of the variant. 

The Mu strain is the seventh variant of the original COVID-19 detected in Japan, alongside the alpha, beta, delta, gamma, kappa, and lambda.

While the Delta variant had dominated new COVID-19 infections in the country, sub mutation of it had also emerged domestically this week, Japan Times reported on August 31.

Following the Mu variant’s presence, Japan becomes the 40th country that has it. 

In WHO’s announcement about the strain, cases of the variant were most rampant in Colombia and Ecuador. 

“Variants of interest” is the second-highest level in WHO’s classification of variants. 

Early data suggested this Mu version of the original coronavirus may have a similar ability to escape immunization as Beta, but research was still at a juvenile stage. 

“The Mu variant has a constellation of mutations that indicate potential properties of immune escape,” WHO’s weekly bulletin on the pandemic said. The concern is that vaccines and antibody therapies against the Mu strain may not be as effective as against the original COVID-19.

Nonetheless, the severity of the risk posed by the Mu variant will be determined by whether instances rise considerably in the coming weeks and months.

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