Giery said the donor wasn't tested for rabies because his symptoms didn't raise a red flag for infection.

NPR: NC Airman At Center Of Rabies Case Was Outdoorsman

If you fit the IBS criteria and don't have any red flag signs or symptoms, your doctor may suggest a course of treatment without doing additional testing.

CNN: Irritable bowel syndrome

"I don't want it to be a huge red flag, " she says.

WSJ: Turning That Layoff Into Career Catalyst

She even suggests putting a red flag on your desk to warn colleagues that you don't want to be disturbed.

BBC: Go Home On Time