How long can infectious diseases live outside the body if in a needle?

Likely not long.: In order to get infected this way, the disease would likely have been in some fluid that would be injected in the body quite rapidly, and at that time contaminate the needle. The needle would not be used again but discarded. Most needles are disposable now so they should be sterile before use. If in a needle, the disease would only live likely <1-20 min. As germs don't live long on metals, etc.