Further doubts have been cast over the Olympic Games in Tokyo owing to a new wave of Covid-19 cases and spread of virus mutations across the host nation.

With the Games just months away, scheduled to take place from July 23 to August 8, Japanese prime minister Yoshihide Suga declared a state of emergency in the city of Osaka — effective today — as a result sudden spike in cases.

He also refused to rule out enforcing and expanding emergency measures in other cities, including Tokyo, in an effort to contain infections.

“All possibilities are being considered,” he told local media yesterday. “It doesn’t matter specifically where; we will act without hesitation if needed.”

As well as being forced to grapple with the new wave of infections, health experts have raised particular concern about the spread of mutant strains, especially as large-scale vaccinations of the general population have not yet begun.

As of yesterday, 355 new infections were reported in Tokyo, while a total of 594 new coronavirus cases were reported in Osaka, a day after a record 666 were confirmed.

Most worryingly for local health officials, variants of the virus, which have cropped up around the world since last year, including the E484 mutation, has been detected in a growing number of cases in Tokyo.

About 70 per cent of coronavirus patients tested at a Tokyo hospital last month carried the E484K mutation, which in some cases is reportedly known for reducing vaccine protection.

The mutation was found in ten of 14 people who tested positive for the virus at Tokyo Medical and Dental University Medical Hospital in March, the report said.

For the two months through March, 12 of 36 Covid-19 patients who carried the mutation, none of them had recently travelled abroad or reported contact with people who had.

Despite the latest setback, and while the pandemic will almost certainly still be ongoing by July, the Japanese Government and International Olympic Committee are determined to hold the Games as scheduled.

Tokyo 2020, which will keep its name despite the delay, will be a very different event from a typical Olympics. Overseas spectators will not be allowed to attend, masks and temperature checks will be required, and athletes will be barred from socialising with their international competitors. Participants, however, will not be required to be vaccinated.

Roughly 80 per cent of Japanese citizens polled in January said they want the Olympics to be postponed again or cancelled altogether, while officials and organisers continue to face overwhelming public pessimism in the host country.

Demonstrations and protests broke out in front of the headquarters of Tokyo 2020 last month in light of a perceived feeling among the public that Japan’s national coronavirus vaccination programme is lagging behind those of other advanced countries.

Banners and placards reading "Cancel the Olympics!" were held up by demonstrators while their chants reportedly could be heard through the streets.

Amid the continued uncertainty, the start of the Tokyo Olympic torch relay was officially kicked off in a small, socially distanced ceremony late last month.

The prestigious event in Fukushima, acted as the official countdown to the postponed Games, and will see an expected 10,000 bearers carrying the torch across Japan to the opening ceremony on July 23.