The young man arrived at the clinic with a laceration down his back—an injury he’d suffered while mountain biking. After suturing his wound and administering painkillers and antibiotics, nurses left him for 30 minutes of observation. Moments later, he began itching and broke into hives. He was going into anaphylactic shock.

The patient, in this instance, was a hologram. The nurses were students at San Diego State University and Texas Tech University Health Sciences Center. And the man’s allergic reaction was one of 10 scenarios...