The Japan Rugby Football Union said Thursday that the start of the 2021 Japan Rugby Top League season will be pushed back to early or mid-February and that the competition format will be modified because of multiple COVID-19 outbreaks among players and staff.

The decision was made after 18 new coronavirus cases among three teams were confirmed on Thursday, two days after 44 people from three teams tested positive for the virus, casting doubt over the league's ability to operate safely in a pandemic.

"We still have players that have to be retested or confirmed as having had close contact with those infected, and it is difficult to hold matches under such circumstances," Top League Chairman Osamu Ota said. "We made our decision as it will impact next week's fixtures too."

"We cannot deny the possibility of there being more infections in February, but there are more teams with no infection. We feel it is not impossible to have zero cases by then and will communicate closely with teams as to why some are not doing as well (as others)."

The first stage of Japan's top-tier domestic rugby union competition was scheduled to start with five games on Saturday and three on Sunday, but the JRFU had to cancel two contests earlier in the week because of the initial outbreak.

On Tuesday, the JFRU said 24 players and staff at Canon Eagles, 13 from Toyota Verblitz and seven from Suntory Sungoliath tested positive in preseason screening without revealing any identities.

Through Thursday, five positive cases were also reported by Toshiba Brave Lupus, 10 by Kobe Kobelco Steelers and three by NEC Green Rockets to take the total tally to 62.

In addition there have been eight positive tests at Top Challenge League side Toyota Industries Shuttles, though the JRFU refused to comment on whether the start of the second division would also be delayed.

The Top League said the priority is to hold a complete season as standings from this year's competition will decide which divisions teams are placed in when the sport's new professional league is launched in 2022.

As such it is hoping to get things under way by the middle of February with an adjusted format that sees the 16 Top League teams play the same first stage of round-robin games in two groups of eight.

Rather than a second stage of pool games, the sides will then be joined by the top four teams in the Top Challenge League in a 20-team knockout competition.

However, Ota stressed that three other scenarios have also been planned for should there be any further delays due to the coronavirus.

"We are still hoping to finish the season on May 23," he said, as the league hopes to allow the national team to prepare for its summer games, including the June 26 fixture against the British and Irish Lions in Scotland.

Ota and JRFU Chairman Kensuke Iwabuchi stressed that COVID protocols were the teams' own responsibility.

But they were hopeful, despite the recent rise in positive cases, that a full season can still be completed, allowing for a smooth transition to the new professional league, not to mention make up for 2020, when the season was canceled after just six rounds because of the pandemic.

However, some venues in the first-stage would have to be changed, they said, and it would be unlikely that the National Stadium, which was set to host the Toshiba vs NTT Communications Shining Arcs game this Saturday as a trial run for Tokyo 2020 organizers, would be available.