Almost 100-year-old mom tests positive for COVID but no symptoms. Anyone else have this experience?

Mom will be 100 in October. She was diagnosed with dementia in 2008, and now resides in memory care. She has tested positive for COVID repeatedly, but has never shown a single symptom -- no cough, no fever. She is, of course, in quarantine, so I have to visit her through a window or, weather permitting, a fence, which I do daily. Has anyone had this experience, or even heard of someone this old testing positive and showing no symptoms?