The Tokyo Olympics could cause a new strain of coronavirus if the games go ahead this summer, an expert has said.
Dr Naoto Ueyama, head of the Japan Doctors Union, said the International Olympic Committee (IOC) and the Japanese government had underestimated the risks of bringing 15,000 Olympic and Paralympic athletes into the country, along with thousands of officials and media from more than 200 countries.
He told a news conference today: "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."
Japan has pledged to hold a "safe and secure" 2020 Olympics in Tokyo after a year-long postponement but it is struggling to contain a fourth wave of infections and preparing to extend a state of emergency in much of the country.
Japanese officials, Olympics organisers and the IOC have all vowed the Games will go ahead, albeit under strict virus-prevention measures. Foreign spectators have been banned and a decision on domestic ones is expected next month.
But even with those steps, worries remain about the influx of athletes and officials into Japan, where a vaccination drive remains glacially slow, with just over 5 per cent of the population having had a jab.
However, Kenji Shibuya, director of the Institute of Population Health at Kings College, London, who has recently been helping the vaccination campaign in Japan, played down dangers specific to the Games.
"Mutation takes place when virus stays in immunocompromised or partially immunised people for a long period of time," Prof Shibuya said.
"So the current situation in Japan is more dangerous than (during) the Tokyo Games, in my opinion."
The government is currently preparing to extend a state of emergency across much of the nation originally set to be lifted on May 31, most likely well into June, officials have said - just weeks before the Games are set to open on July 23.
But IOC member John Coates has said the Olympics could be held even under a state of emergency, an opinion Dr Ueyama said was infuriating.
"In regards to these statements, the people of Japan are indeed holding great anger towards this, and this is even more the case for healthcare and medical professionals.”
Additional reporting by agencies