The NBA has announced that all matches will be suspended from Thursday until further notice, after a Utah Jazz player tested positive for coronavirus.
The announcement was made just before the Jazz game against the Oklahoma Thunder was due to start on Wednesday.
The NBA said the player who tested positive was not at the game.
“The NBA will use this hiatus to determine next steps for moving forward in regard to the coronavirus pandemic,” a statement said.
The Jazz v Thunder game was postponed.
Unconfirmed reports say the player concerned was Frenchman Rudy Gobert.
The Jazz said a player tested negative for influenza and a respiratory infection, and then tested positive for Covid-19, the current strain of coronavirus.
Orlando Magic player Evan Fournier later tweeted about his compatriot, 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.”