Dr Ueyama told a news conference on Tuesday: "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. "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."