A friend of a friend recently asked if she could stay a couple of days with us, as she was going to an event within easy reach of our house. We made her welcome, and spent some time with her.
The morning she left she was coughing, and when I asked if there was anything I could do to help, she said she'd had a virus for several days and it had probably got worse because of travelling, but she'd be ok. She hadn't shown any symptoms that I\d recognised.
I caught the virus, which knocked me down for most of a week, and passed it on to DH was was ill for the next week. Obviously not as fit as our visitor! We both have health conditions, which she knew about.
If I was carrying an infectious disease, even a minor one such as a cold, I'd always let my host know in advance and wear a mask. In fact, wouldn't stay with people unless I had to.
AIBU to expect others to do the same?