My husband to me he uses a toilet that has a pee on the seat cover but he wipes using tissue, after a day so he saw a blister in his penis. He is really afraid what it is. And later he found out that the uses that toilet before him was a co-worker with STD. Is STD transferable through urine left in the toilet because my husband says his penis maybe touch the seat cover when poop...We are really worried about it, and we don't know what it is...please help.