Kentaro Iwata, a professor of infectious diseases at Kobe University, said that he doubts the Tokyo Olympics will go ahead in 2021, even after being delayed a year by the IOC.

"Japan might be able to control this disease by next summer...but I don't think that would happen everywhere on earth," Iwata said in an online press conference arranged by the Foreign Correspondents' Club of Japan.

"I'm very pessimistic...unless you hold the Olympic Games in total different structures, such as no audience or a very limited participation," he said.

Further delays would throw the sporting calendar into even greater chaos, given the flexibility required over age restrictions, qualifications and broadcasting considerations.

Iwata maintained that the Japanese government is still too slow to react to the pandemic and that many other countries have reacted worse.

"The most effective way of stopping further transmission is a so-called lockdown," he said, noting that he "can't be really that optimistic" about potential vaccines emerging over that time period, given the extensive testing that has to take place.