I’m sorry that you became ill.
It’s entirely possible that you became ill that quickly like that, and from someone who went ill to Mass like that.
As I have mentioned previously, people are not always aware of how viruses and other illnesses are spread.
They assume that something is just “a little cold,” so it’s alright to go out in public with it.
Another person can become really ill from someone else’s “little cold.”
I’m one of those people who have ended up with either bronchitis or pneumonia, from that “little cold” or “minor sniffle” that someone else decided to go out into public with while they were still in the contagious stage with it, where I was really sick for months afterwards.
Virus droplets spread in the air, and get on surfaces that we then touch when we’re ill and contagious, and then someone else touches them, and we can also breathe them in, too.
A cold is also contagious when someone has it for the first few days that they have it.
I have become ill from having someone cough or sneeze on me, too.