All major sport in the United States has been suspended amid the coronavirus outbreak.
The NBA has announced that all matches will be suspended from Thursday until further notice, after a Utah Jazz player Rudy Gobert tested positive.
The NHL and MLS later announced the stoppage of its respective seasons, the latter for 30 days.
The MLB has delayed the start of its 2020 season by at least two weeks due to the "national emergency".
The other major US sports league - the NFL - is currently in its off-season, although the 2020 Draft in Las Vegas is scheduled to start on 23 April.
Men's and women's college basketball has also been cancelled, just a day after it was announced it would initially continue without spectators.
The NCAA, the governing body of US college sport, announced the Division I men's and women's tournaments would be cancelled, in addition to remaining winter and spring NCAA tournaments.
The Division I men's basketball tournament, known as March Madness, is one of the biggest and most popular sports events in the United States.
Gobert apologises to 'people he may have endangered'
The NBA's announcement was made just before the Jazz game against the Oklahoma Thunder was due to start on Wednesday.
The NBA said Gobert was not at the game, which was postponed, but the Frenchman has since had to issue an apology for potentially exposing others to the virus.
Earlier this week, he jokingly touched reporters' microphones and dictaphones at a pre-match news conference.
"I have gone through so many emotions since learning of my diagnosis, mostly fear, anxiety, and embarrassment," he wrote on Instagram.
"The first and most important thing is I would like to publicly apologise to the people that I may have endangered. At the time, I had no idea I was even infected. I was careless and make no excuse.
"I hope my story serves as a warning and causes everyone to take this seriously."
In a statement, the NBA said: "The NBA will use this hiatus to determine next steps for moving forward in regard to the coronavirus pandemic."
Orlando Magic player Evan Fournier tweeted about Gobert after the news of his diagnosis broke, writing: "Was just on the phone with Rudy. He is doing good man. Let's not panic, everyone."
The owner of the Dallas Mavericks, Mark Cuban, heard about the NBA decision at the game with the Denver Nuggets on Wednesday evening.
"I thought this is crazy. It can't be true," he said. "It is like out of a movie. Unreal.
"It is not about basketball and money. This is exploding to the point where I think about the families. We are making sure we are doing this the right way."
Detroit Pistons coach Dwayne Casey called it "unprecedented", while Miami Heat coach Erik Spoelstra said he was "stunned".
"It's a very serious time right now. I think the league moved appropriately," Spoelstra added.
Prior to the NBA announcement, the Golden State Warriors were set to play their home game against the Brooklyn Nets on Thursday behind closed doors.
That was prompted by ban in San Francisco on mass gatherings of more than 1,000 people for at least the next two weeks in a bid to slow the spread of coronavirus.
In the past, NBA seasons have been delayed - the schedule was shortened in 1998-99 and 2011-12 because of protracted negotiations over a new collective bargaining agreement - but it has never before been suspended while in progress.
There are five weeks remaining in the regular season with the play-offs due to begin on 18 April.
If the season does not resume it could mean Atlanta Hawks forward Vince Carter has played his final NBA game.
The 43-year-old, who was retiring at the end of this season, is the first NBA player to have a career spanning four decades.
"It's a weird way to say I'm calling it a career. It really is," Carter said after the Hawks' 136-131 loss to the New York Knicks on Wednesday. "I have 15 games left, technically. But if not, I'm one with it."