Japanese authorities announced that the country’s borders will be closed to all foreign visitors from December 28 until the end of January, after a new strain of COVID-19 virus was found in foreign nationals who had traveled from the UK. The announced measures are the harshest restrictions yet instituted in response to the new virus threat.

Japanese nationals and foreigners living in Japan will still be permitted to return to the country, Japanese financial daily Nikkei has reported, citing the government’s declaration.

At least five people traveling from Britain to Japan have been confirmed as infected with the new strain of the virus, which goes by the technical name SARS-CoV-2 VOC 202012/01.