What should you do if someone you live with might have ?

I am living with a bunch of students, and i think one of my housemates has . Every now and then she has a red bump on her upper lip and has scar tissue as if she was cut. We share cutlery. And i try to rinse whatever i use with hot water before using it but what should i do to prevent myself from catching it, and not be mean at the same time. And i dont think she knows she has .