TOKYO: The mu variant of the novel coronavirus has been detected from two women who tested positive for the virus in June and July upon arriving in Japan, the health ministry has said.

It is the first time for the mutated strain, first reported in Colombia in January, to have been detected in Japan. The World Health Organization late last month classified it as a variant requiring attention. The ministry will investigate details of the variant, including the level of its transmissibility.

One of the two women, in her 40s, arrived at Narita International Airport in Chiba Prefecture, east of Tokyo, June 26, according to the ministry. She had been to the United Arab Emirates. The other woman, in her 50s, who had stayed in Britain, flew to Tokyo International Airport at Haneda July 5.

Both women did not show any COVID-19 symptoms.

Their infections were confirmed after the National Institute of Infectious Diseases, following the WHO’s classification of the strain, re-examined genome analysis results of people who had tested positive for the novel coronavirus in quarantine checks at Japanese airports.