Japan was working with other nations, the World Health Organisation and other medical experts to analyse the new version of the virus, and it was still unclear whether available vaccines would work.
Japan's Ministry of Health said the four passengers had arrived in Japan on January 2. Three had shown symptoms such as difficulty breathing, fever and sore throat.
"I understand a new variant that is different from Britain's and South Africa's has been found", Wakita told a health ministry briefing.
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Ontario NDP Leader Andrea Horwath says that the Premier should be releasing those modelling numbers today. The cumulative average incidence rate in the province is 1,425 cases per 100,000 people in Ontario.
Available information about the new strain is now restricted to its genetic make-up and it is not possible yet to determine how infectious it is.
The latest COVID-19 variant is different from that recently identified in the United Kingdom and South Africa.
Since the start of the pandemic, Japan has recorded more than 283,000 infections and over 3,800 deaths related to the coronavirus.
On Thursday, Prime Minister Yoshihide Suga declared a monthlong state of emergency for Tokyo and neighbouring prefectures Chiba, Kanagawa and Saitama, which took effect Friday. JapanMeanwhile, is in the midst of its own Worst coronavirus wave ever encountered.