The NCAA canceled its men's and women's basketball tournaments on Thursday because of the spread of coronavirus, putting an abrupt end to the season less than a month before champions were to be crowned.

The unprecedented move comes a day after the NCAA announced the games that were scheduled to start next week would go on, but played in mostly empty arenas. That plan was scrapped as every major American sports league from the NBA to MLB put the brakes on its season due to concerns about the pandemic.

"This decision is based on the evolving COVID-19 public health threat, our ability to ensure the events do not contribute to the spread of the pandemic and the impracticality of hosting such events at any time during the academic year given the ongoing decisions by other entities," the NCAA said in statement.

The NCAA canceled championships in every spring sport, which include hockey, baseball and lacrosse.

The stunning end to the basketball season came about four hours after a frantic morning when conference tournaments around the country came to a sudden halt. Moments away from tipoff at some arenas, and minutes apart, each Power Five conference canceled its remaining games.

At Madison Square Garden in New York, the Big East game between Creighton and St. John's did start, but at halftime the conference called off that game and all the rest. Turns out that was the last Division I basketball to be played this season.

Smaller conferences followed suit, shutting down their tournaments, and within a few hours 58 men's games scheduled in 16 conferences had been canceled.

Then the conferences began shutting down all athletic activities, for at least a few weeks like the Southeastern Conference, or indefinitely like the Atlantic Coast Conference.

A few hours later, the NCAA put an end to it all.

The decision to cancel baseball and softball drew a sharp response from SEC commissioner Greg Sankey.

"Surprised that we've made a decision now in mid-March to not play baseball or softball national championship events [scheduled for June]. So I look forward to learning what informed that decision. I know what's informed our decisions over the last day and a half or so, but the news from the NCAA we were waiting on -- on the basketball tournaments and some of the championships happening now -- but obviously, there was the decision to go further," Sankey said on The Paul Finebaum Show.

For most people, the new coronavirus causes only mild or moderate symptoms, such as fever and cough. For some, especially older adults and people with existing health problems, it can cause more severe illness, including pneumonia. The vast majority of people recover from the virus.

The NCAA men's basketball tournament has been played every year since 1939 when Oregon won the championship in Evanston, Illinois. It has grown through the years, both in size and stature. The three-week tournament generates almost a billion dollars in revenue each year for the NCAA and its hundreds of member universities and colleges, most coming from a television contract with CBS and Turner that pays the NCAA almost $800 million annually.

It is now one of the biggest events in American sports, a basketball marathon of buzzer-beaters, upset and thrills involving 68 teams. The field for the men's tournament was scheduled to be announced Sunday, creating the famous bracket that sports fans would obsess over in office pools and at sportsbooks.

The 64-team women's field was to be revealed Monday.

"This is a difficult time with so many conflicting emotions," Dawn Staley, coach of the No. 1-ranked South Carolina women's basketball team, said in a statement. "First and foremost, we have to recognize how important it is to do the right thing for our community. Sports is a big part of our lives, but just one part of how we are connected to each other. We need to step back and think about the larger good served by canceling events that put people at risk.

"As competitors, we are certainly disappointed that we will not have the opportunity to contend for a second National Championship. That said, it will not diminish the way we look at our season, how we value our body of work over the last four months. We have measured ourselves against the best in the country over that time, and will embrace and relish that accomplishment."

The NCAA women's tournament began in 1982 and it, too, has become a big event, raising the profile of the sport.

"I'm disappointed but I totally understand. I really feel for the senior student-athletes; every student athlete, but particularly the seniors because this is their last chance for the fans," said Oregon women's coach Kelly Graves, whose team would have entered the tournament as favorites to reach the Final Four in New Orleans. "There's something more important than the games going on. I've kind of come to grips to that a little more than a few hours ago."

Games would have started on the men's side on Tuesday in Dayton, Ohio, before spreading out to eight sites from coast-to-coast from next Thursday through Sunday. The women's tournament was scheduled to begin March 20, with first- and second-round games to be played at 16 sites on or near the campuses of the top teams.

The men's Final Four was to be played April 4 and 6 at Mercedes-Benz Stadium in Atlanta. The semifinals and final typically pack football stadiums for the games, and after the champion is crowned the best moments of the year's tournament are wrapped up into the "One Shining Moment" montage that has become a staple of CBS' television coverage through the years.

Instead, March Madness took on a different meaning as sports have virtually shut down.

Baseball's College World Series not be held for the first time since 1946. Omaha has hosted the Division I baseball championship every year since 1950. The CWS has a $70 million annual impact on the local economy each year and produces 10 days of programming inventory for ESPN.

"Devastating. Stunning," UCLA baseball coach John Savage said. "I feel for all the players. I feel for the coaches. I feel for all the programs that work so hard through the fall and January."

The eight-team College World Series is held each June at TD Ameritrade Park and is the culmination of the NCAA baseball tournament, the No. 2 revenue producer for the NCAA. The event draws more than 300,000 fans per year from across the country and is one of Omaha's most anticipated events of the year.

"To have such a decision to go down so quickly is just really hard to imagine," Savage said. I "feel for the seniors across the country. It's just a really, really sad day."

Information from The Associated Press was used in this report.