A COVID-19 cluster at a Japanese hotel where dozens of Brazilian Olympic team members are staying raised new concerns about infections at the Tokyo Games, as the host city recorded its highest number of new cases for six months.
Just over a week before the opening ceremony, the spreading infections highlight the risks of staging the world's biggest sports event during a pandemic even without spectators in sports venues.
Seven staff at the hotel in Hamamatsu city, southwest of Tokyo, had tested positive for the coronavirus, a city official said.
But a 31-strong Brazilian Olympic delegation, which includes judo athletes, are in a "bubble" in the hotel and separated from other guests and have not been infected.
The Russian women's rugby sevens team were also in isolation after their masseur tested positive for COVID-19, the RIA news agency reported from Moscow -- as was part of the South African men's rugby team after a case on their inbound flight.
Highly contagious virus variants have fuelled the latest wave of infections, and failure to vaccinate people faster has left Japan's population vulnerable.
Tokyo, where a state of emergency has been imposed until after the Games end on August 8, recorded 1,149 new COVID-19 cases on Wednesday, the most since Jan. 22.
Officials have imposed Olympic "bubbles" in an effort to keep out COVID-19, but medical experts are worried that they might not be completely tight as movement of staff servicing the Games can create opportunities for infection.
The Olympics, postponed last year as the virus was spreading around the world, have lost much public support in Japan because of fears they will trigger a surge of infections.
International Olympic Committee (IOC) President Thomas Bach praised organisers and the Japanese people for staging the event in the midst of the pandemic.
"These will be historic Olympic Games ... for the way how the Japanese people overcame so many challenges in the last couple of years,," Bach told reporters after meeting Prime Minister Yoshihide Suga.
When Japan was awarded the Games in 2013, they were expected to be a celebration of recovery from a deadly earthquake, tsunami and nuclear accident in 2011.
Japanese leaders had also hoped the re-scheduled Games this year would help mark a global victory over the coronavirus, but many countries are now struggling with new surges in infections.
Many Olympic delegations are already in Japan and several athletes have tested positive upon arrival.
The refugee Olympic team has delayed its travel to Japan after a team official tested positive in Qatar, the International Olympic Committee said.
Twenty-one members of the South African rugby team were isolation as they are believed to have been in close contact with the case on their flight, said Kagoshima city, which is hosting the team.
They were due to stay in the city from Wednesday, but that plan has been halted until further advice from health authorities, said city official Tsuyoshi Kajihara.
Global interest in the Tokyo Olympics is muted, an Ipsos poll of 28 countries showed, amid concerns over COVID-19 in Japan and withdrawals of high-profile athletes.
With spectators barred from all Olympic events in Tokyo and surrounding regions, officials are asking people to watch on television and keep their movements to a minimum.
Among those will not be competing in Japan is former world number one golfer Adam Scott, who questioned whether holding the Tokyo Olympics was a responsible decision.
Switzerland's Roger Federer became the latest big name in tennis to withdraw, the 20-times Grand Slam champion saying on Tuesday he had picked up a knee injury during the grasscourt season.