Sounds like your immune system has been going to war big time on this. I hope you continue to improve. It's definitely risky business with your asthma. Scary stuff.
You're probably right about picking it up at the supermarket. It's all very well keeping your distance from one another, but when everyone's touching what's on the shelves, it's going end up being shared around and short of fumigating everything, I don't see how you can be completely clear, especially with fresh foods.