I suspect a great many have had Covid and not known it. I would have brushed off the “hrmmm, I might be coming down with something” feeling (which lasted 2 weeks, then left) had I not been a heart patient, and not sniffed a smelly candle tipping off my otherwise unnoticed loss of smell. I tested positive; wife didn’t get tested for it per se, but did test as having the antibodies later.