Well. there are "healthy" people who have underlying medical conditions they never know about. It certainly seems those are very much in the minority.
Contagion levels aren't necessarily a problem. A virus causing a bad cold may be contagious but with low "payload", for example; yes, can trigger asthma and other things...
Mercedes F1 and medical colleges have been working on some systems which would mean ventilators can be reserved for the most serious cases only.