The only way to get hiv is to have a trade of fluids, you are in no risk from a door knob. And if ur masturbating in a public restroom you need to learn control.

Thanks for your reply. Ok, let's suppose the following situation: the previous user of the toilet before me was hiv and he soiled the doorknob with his sperm. I touched the doorknob after 5 minutes and after that I touched my penis. Is there risk in that situation? How long time does it take for the virus to die outside the human body?

Someone will give me an answer?

I took an emt class....And they told me once hiv was exposed to air it died within seconds..Unlike other viruses like hepatitis....I would talk to you dr if you are that scared.

Thanks for your reply. In that case, how is possible to get hiv through using unsterilized needles if the virus dies so fast? The needle exchange should be very fast to be able to infect, right?
And why they need to test the blood when the virus dies so fast? If a hiv
person gave his/her blood for transfusion a lot of time will be passed until it is transfused to someone else, therefore enough time for the virus to die. Then why do they need to test it?