They might not need to go to the hospital or are dying, but they are sick and will be home for a minimum or two weeks regardless.
My 35 year old sister, who is in perfect health and is a nurse, has had a 101 degree fever, has the dry cough and says her lungs feel like they are caving in, is waiting for her test results to come back after being tested on Monday for the virus. It will take 5-6 days she says to get the results back. If she's positive, she'll have to be in quarantine even after she feels better.
How many people did she come in contact before she was showing symptoms? She feels pretty strongly she got this at the hospital as she only worked, got off her shift, worked the coronavirus hotline and went home. Just because someone young abd arent showing symptoms early on doesn't mean they aren't carrying the virus.