Have you ever looked at a seemingly clean surface with a UV light? It's surprising how much invisible ick there is, and it pops out since it visibly fluoresces. This might be a useful way to see the spills?
However, those lights are usually handheld and small. Expecting cleaning staff to cover 100% of all walls each time they cleaned it (which is multiple times a day) is prone to failure.
Plus those lights work best when the room is dark. Which means you could only clean it at night.
And some rooms have multiple patients, so now the cleaner people will need to work around them / have them be OK with the room being dark for a while. This can work, but again not every patient will be comfortable with a "crime scene investigation" happening while they recover.
Think viable transmission vectors for those diseases.