The first wave of Covid-19 saw professional sport grind to a halt as countries across the world imposed lockdowns.
With cases on the rise again, particularly in England, some sports – including football, rugby union, boxing and snooker – have already been disrupted.
So how is elite sport in 2021 being affected by the pandemic here and overseas?
And are Premier League football, the Tokyo Olympics, England’s cricket in Sri Lanka and the British and Irish Lions tour of South Africa in danger of being delayed or cancelled?
An increasing number of fixtures had to be postponed due to Covid outbreaks in December, particularly lower down the English football pyramid.
Despite that, and more nationwide restrictions, Prime Minister Boris Johnson confirmed on Monday that elite sport could continue.
That means six tiers of men’s football from the Premier League down to the National League North and South are going ahead.
The FA Cup and Carabao Cup will also continue to be played.
Women’s elite football – the Women’s Super League and Championship – may also go on.
The Women’s FA Cup has been halted, however, as it has not yet reached round three, when elite teams join.
All fixtures are taking place without fans.
The British and Irish Lions tour to South Africa this summer has been plunged into fresh doubt by the rise in cases in both places.
Lions chiefs issued a statement on Sunday saying they were in “constant dialogue” about the viability of the trip in July and August.
They added: “We are very aware of the need to make a timely decision on the best way forward; not least so that we can provide clarity to supporters booked to travel to South Africa next summer, or those thinking of making the trip.”
Talks are set to continue this month and possibly into February while the situation is assessed.
Six Nations organisers, meanwhile, say they are planning to go ahead with the tournament, which starts on 6 February.
One possible solution would be to delay the competition until the summer if the Lions tour is shelved.
“The Six Nations is planning for the tournament to go ahead as scheduled, but we are are monitoring the situation with the unions and their respective governments and health authorities,” said a spokesperson.
If it goes ahead, England’s opener against Scotland would be played behind closed doors.
In the meantime, domestic rugby can continue without spectators in the Premiership and Championship, which will return in March.
England’s tour of Sri Lanka is also in doubt after Moeen Ali tested positive on arrival earlier this week.
As it stands, the two-Test series is set to go ahead as planned on 14 January in Galle, but further Covid cases would jeopardise that.
All-rounder Ali must quarantine for 10 days, while team-mate Chris Woakes is also isolating because they shared a vehicle to the airport.
England are undertaking further tests on Tuesday and hope to start training on Wednesday.
The tour was originally scheduled for last year but postponed during the first Covid outbreak.
Both Test matches in Galle will be played behind closed doors.
England are due to visit India in February and March for matches in all formats.
Olympics and Paralympics
Foreigners are currently prohibited from entering Japan amid a surge in cases linked to the new variant of Covid-19.
Prime Minister Yoshihide Suga insisted on 1 January, however, that the Olympics would not be delayed for a second time.
The Olympics are due to begin on 23 July and the Paralympics on 24 August.
The Australian Grand Prix, the first race of the 2021 Formula 1 season, looks increasingly likely to be postponed.
The race in Melbourne on 21 March is expected to be moved to later in the year, with the Bahrain Grand Prix on 28 March opening the new campaign instead.
Strict local entry conditions mean arrivals in Melbourne must quarantine for 14 days.
Given the time it takes to prepare for races, that would require all teams to travel three weeks in advance.
However, that would clash with F1’s only scheduled pre-season test from 2-4 March in Barcelona.
Melbourne is also due to stage the first tennis Grand Slam of the 2021 season, the Australian Open.
The tournament has already been pushed back from mid-January to 8 February to allow players time to quarantine on arrival.
All boxing in Britain has been postponed until February at the earliest, officials said at the weekend.
Fights affected include Lee McGregor’s European bantamweight title fight against Karim Guerfi on 22 January.
Welterweight Josh Kelly’s European title clash with David Avanesyan on 30 January is also off.
The Masters will go ahead next week as scheduled, albeit with a change of venue.
The sport’s biggest invitational tournament has been switched from its traditional home of Alexandra Palace in London to the Marshall Arena in Milton Keynes.
The venue has staged seven of the last eight events on the World Snooker circuit as it is considered better suited to maintaining a secure bubble.