LAS VEGAS — Hand-sanitizing dispensers stationed outside locker rooms and along arena concourses. Workers wearing rubber gloves and spritzing hand railings with disinfectant up and down aisles while games are going on. Players keeping a healthy distance — no selfies or slapping hands — from the fans who traveled far to cheer them.

Over the last week, the epicenter of this new and evolving normal in college basketball has been Las Vegas, where four conferences — the Pacific-12, West Coast, Mountain West and Western Athletic — are holding their men’s and women’s basketball tournaments.

These are the types of events that public health officials say are anathema to containing the virus, which has spread from China through Europe and to the United States. On Wednesday, the N.C.A.A., faced with an epidemic, announced that it would play its men’s and women’s basketball tournaments, which brought in close to $1 billion in revenue last year, without spectators at the host arenas this year.

The eight tournaments here, four men’s and four women’s, consist of teams from 39 schools and 13 states. They have brought tens of thousands of fans into close contact at arenas, hotels and bars, and then, after several days, will disperse them back home.