One year after Covid-19 sent sport across North America grinding to a halt, professional leagues and tours are inching back towards normalcy after absorbing a multi-billion-dollar financial hit.

Twelve months ago on March 11, NBA commissioner Adam Silver sent shockwaves across the sporting world after dramatically halting the season following confirmation of Utah Jazz player Rudy Gobert's positive test.

The NBA decision triggered a domino effect, with baseball, soccer, golf, ice hockey and other sports swiftly following suit either by suspending their seasons or cancelling events altogether.

A year after the start of the shutdown, US leagues are continuing to count the cost of the pandemic as they adjust to the new realities of sport in the age of Covid-19.

The NBA has reached the halfway point of its abbreviated 2020-2021 season after losing an estimated $1.2 billion through its interrupted 2019-2020 campaign, with a $4 billion loss projected for 2020-2021.

NBA chief Silver however is hopeful that the worst may be over, noting that next season may resemble something like a return to normality as more Americans get vaccinated against Covid-19 and fans return to arenas.

"I'm fairly optimistic at this point that we will be able to start on time," Silver said ahead of Sunday's All-Star game.

"If vaccines continue on the pace they are, and they continue to be as effective as they have been against the virus and its variants, we're hopeful that we'll have relatively full arenas next season."

Silver added that despite losses he described as "considerable", the "long-term health of the league is very solid."

Major League Baseball, meanwhile, is also counting the cost of coronavirus. The league slashed its 2020 season from 162 games to 60, finally starting in late July before wrapping the World Series in October.

Although fans were allowed to return for the late stages of last year's playoffs, regular season games in 2020 took place in empty arenas, denying clubs game day revenue and contributing to collective losses estimated by MLB Commissioner Rob Manfred at around $2.8-$3 billion.

A full 162-game regular season is planned when the 2021 campaign gets under way on April 1, but spectator access will vary depending on city and state health regulations where each team is based.

The World Series champion Los Angeles Dodgers will only be allowed a maximum of 100 fans at Dodger Stadium under current rules; the St. Louis Cardinals have been approved to allow 14,500 spectators.

Major League Soccer is bracing for another hefty financial loss after taking a $1 billion hit in 2020.

MLS was halted just two weeks into its new season last year, returning with a tournament staged in a bubble in environment in Florida before the regular season resumed in August.

"We are forecasted to lose pretty close to $1 billion, if not $1 billion (exactly), that we have been talking about," Garber said in February. "When you don't have fans for the majority of your season, it's just pure math."

The National Football League, meanwhile, provided a template for professional leagues in North America by completing its season in February with the Super Bowl in Tampa.

A robust testing program and strict health and safety protocols allowed the league to fulfill all of its 256 regular season games and playoff schedule successfully.

A crowd of 25,000 fans, including several thousand vaccinated healthcare workers invited as guests, attended last month's Super Bowl, but NFL Commissioner Roger Goodell admits it is unclear what fan attendance may look like when the 2021 season kicks off next September.

"One of the things that I think I have learned and I think all of us have learned is try not to project too far in advance because it's difficult to do," Goodell said. "I know this: We've learned to operate in a very difficult environment. We have found solutions, and we'll do it again."

Zach Binney, an epidemiologist at Oxford College of Emory University in Atlanta, believes that major US sports "did some really good things" as they plotted a return from Covid-19.

"The NBA, Major League Baseball and the NFL all found various ways to bring sports back without having a lot of cases among their players and staff," Binney told AFP. "The various models were quite strong on that front."

Binney noted however that some NFL and college football teams allowed large numbers of fans back into arenas before being certain it was safe to do so.

"I think they were reckless and got lucky," Binney said.

Other aspects of the US sporting landscape, meanwhile, shifted in more profound ways by the pandemic.

In almost every major sport, television ratings were down sharply, sometimes by striking margins.

The NBA finals ratings nosedived by 51%, while the battle for ice hockey's Stanley Cup cratered by 61%. The US Open tennis tournament slumped by 45% and even February's dream NFL Super Bowl pitting Tom Brady against Patrick Mahomes drew its lowest audience since 2006.

In college sports meanwhile, budget shortfalls caused by the pandemic have led to the elimination of more than 350 sports programs -- the vast majority in Olympic sports including athletics, swimming and volleyball.

Coronavirus