CHICAGO — The serious-faced physicians practice pulling on bulky white suits and helmets that make them look more like astronauts than doctors preparing to fight a deadly enemy. These training sessions at U.S. hospitals on Ebola alert and for health workers heading to Africa can make the reality sink in: Learning how to safely put on and take off the medical armor is crucial.

“When you’re in the real deal, remember to take your time,” biosafety expert John Bivona told doctors during a course this week at the University of Chicago’s medical center. Suits splashed with patients’ vomit or blood must be removed carefully, he explained.

“As much as possible, grab from the inside” to avoid touching contaminated parts of the suits, he said. “Be liberal with disinfectant.”

Looking stoic after this week’s training, Dr. Mark Nunnally said he’s “not overly worried, but I think there’s a legitimate concern” that someone with Ebola may arrive at the hospital’s door.