A steady trickle of cancellations and other disruptions in the sports world caused by the coronavirus outbreak erupted into an avalanche on Wednesday, with the N.B.A. abruptly suspending its season and the N.C.A.A. basketball tournament and other events barring most spectators. A major tennis tournament was also in doubt.

The N.B.A. acted after a player for the Utah Jazz, who had been listed as not playing, tested positive for the coronavirus, causing a moment of confusion before tip-off of a game against the Oklahoma City Thunder. The game was called off and the N.B.A. said the season would go on hiatus indefinitely.

Earlier, the Golden State Warriors had become the first N.B.A. team to bar fans from games because of the coronavirus pandemic, announcing that it would close the doors to spectators for Thursday’s game against the Nets at Chase Center in San Francisco. The move foreshadowed sweeping changes across sports as public officials pressured teams to bar fans to help limit the spread of the virus.

At least 1,190 people in 41 states and Washington, D.C., have tested positive for the coronavirus, according to a New York Times database, and at least 37 patients with the virus have died. A majority of the cases were in Washington State, California and New York.