My husband and bought a 20 year old townhome a month ago--our first
house. Worried that one of my less well trained cats would start
marking his new territory, I bought a black light and checked all
corners a few days ago to see if my fears materialized.

My cat was exonerated. However, the old wallpaper around one of the
toilets had evidence of a human marking their territory (or missing
the target) on many occasions.

Do I have to replace the wallpaper (it superficially looks fine, so I
would rather not bother), or is there a way of sanitizing/cleaning the
wallpaper? The thought of invisible bacteria hiding in the wallpaper
grosses me out and worries me since I have my first child on the way
in January.