What if Tanya's bandage doesn't hide a burn specifically, but her own antibiotic picc line.
She said that the antibiotics didn't work on the slow turner, but what if they got to the person a bit later so they were too far gone. The antibiotics might have slowed it down even more so she extrapolated that they can stop you getting infected.
She might be treating herself and Saul (and maybe Hope without her realising it) because she figured that they slow the spread down.
Michael might even have something under his cast.