Wales' Six Nations match at home to Scotland on Saturday has been postponed because of the coronavirus outbreak.
The two other scheduled games in round five had already been postponed and no dates have been confirmed for completing the 2020 Championship.
The Welsh Rugby Union, which had insisted earlier on Friday the game would go ahead, said it was "in the best interests of supporters, players and staff to fall in line with recent measures taken across the UK and global sports industries".
Several sports have been severely disrupted, with all Premier League and EFL football matches suspended until 3 April.
A WRU statement read: "The Welsh Rugby Union has maintained an open dialogue with, and continued to seek advice and direction from, the Welsh government and other stakeholders, including the Six Nations, on this fast-moving issue.
"Every effort has been made to stage this game and we appreciate that individuals will have been inconvenienced. Given the fluid and unprecedented nature of this issue a postponement became the only viable option."
It added that there would be an announcement on rescheduling the fixture "in the coming days".
Friday's Under-20 Six Nations match between Wales and Scotland in Colwyn Bay will go ahead but will be played behind closed doors.
Meanwhile, Scottish Rugby has suspended all rugby in Scotland for the remainder of March.
A Scottish Rugby spokesperson said: "We have taken on board all expert medical advice before now and we are taking a precautionary approach to give time to assess what the impact of coronavirus will be on Scottish society in the coming weeks before deciding on next steps.
"This decision has been taken with the best interest of everyone involved in the game and in support of the country's work to address the impact of Coronavirus."
The Welsh Rugby Community Game Board will meet on Saturday to discuss the situation relating to grassroots rugby.
The decision comes on a day of widespread sporting postponements worldwide.
- All elite British football has been suspended until 3 April.
- The London Marathon has been moved from 26 April to 4 October, with the Manchester and Brighton Marathons also postponed.
- Golf's opening major of the year, the Masters, has been postponed.
- Uefa has postponed next week's Champions League and Europa League fixtures.
- Also in rugby union, Sunday's Premiership Cup final between Sale and Harlequins.
- Cycling's Giro d'Italia, scheduled to start in Hungary in May, has been called off.
- England's Test cricket series in Sri Lanka has been cancelled.
- Formula 1 has called off the Vietnam Grand Prix on 5 April.
- Formula E is suspended for two months, affecting races in Paris, Seoul and Jakarta.
- Will I get a refund if my event is cancelled?