I did not wear one of the mask nor have I even so much as entered shadowglen since the pandemic started yet I already have the first stage of a virus. Is this a bug? Or do I just have terrible luck?

You have the Baker's Kiss. It's the plot-driven infection given to all non-zombies. It probably will be gone by the end of the plot.

EDIT: Oh, and it's actually the third stage you're on, not the first. You can see all the stages by going here and clicking on Baker's Kiss.

Thanks, that's what I needed to know.