Can STD be contracted from blood on a door knob?

[Writerchris]

Today when opening the door handle at work, I noticed a thin strip of red that looked like it might have been dried blood or possibly some sauce. I have OCD and an axiety disorder, so I've been freaking out (silently) about the chances that I might have touched blood.

If it was blood, can an std...the one that starts with an H.. have been contracted through that. (Sorry my anxiety makes it difficult to type the 3 letters.

I also stupidly tried using a paper towel (while keeping my fingers far away from the spot) to see if it was a pen mark. I was trying to convince myself it wasn't what I thought. Except when I rubbed at the spot a couple times. Part of it flaked off. At that point I throw the paper towel away, while barely holding it.

Sorry for this being so long. What are the chances of getting the std from a door handle that way. Also I was once told that the particular std can survive for 24 hours on a surface and still be contracted if a person touches that surface especially if it's blood.

Is there any truth to that?

Please let me know.

Thanks.