Wimpy Virus. It is important to remember that viruses like hepc, HIV and others are strings of proteins that are connected by very weak bonds. They require many things to stay active and need living cells to reproduce and survive. Unless there was gross blood, mucous or some other organic substance on that needle and it got immediately into you, the odds are very unlikely.
Contaminated needles. Although aids is a horrible and deadly disease, the virus that causes aids, the hiv, is a delicate virus that is killed relatively easily. It does not live very long on a needle that had blood on it, and the virus usually dies when the blood is dried out and old. But, it is best to never share a needle with another human being without being properly sterilized or replaced by a brand new needle.