The head of a Japanese doctors union warned holding the Olympic Games in Tokyo this summer, with tens of thousands of people gathering from around the world, could lead to the development of a new “Olympic” strain of the coronavirus, Reuters reports.

With people from over 200 nations and territories set to arrive in Tokyo, it will be dangerous to host the Games in July, said Naoto Ueyama, head of the Japan Doctors Union.

“All of the different mutant strains of the virus which exist in different places will be concentrated and gathering here in Tokyo. We cannot deny the possibility of even a new strain of the virus potentially emerging after the Olympics,” he told a news conference.

“If such a situation were to arise, it could even mean a Tokyo Olympic strain of the virus being named in this way, which would be a huge tragedy and something which would be the target of criticism even for 100 years.”