Needle sharing

Needle sharing is the colloquialism for the reuse of syringes by multiple illegal drug users to administer intravenous drugs, and is a primary vector for diseases which can be transmitted through blood, including hepatitis and AIDS.

Needle-exchange programmes, a form of harm reduction policy, provide new needles to persons addicted to drugs to help control the spread of disease. However, in the United States, there are three distinct prohibitions on needle exchange programs at the federal level — the Ryan White CARE Act, the Substance Abuse and Mental Health Services Administration (SAMHSA) authorization, and the 1997 Labor-Health and Human Services (HHS) Education appropriations legislation.

Source
Needle Exchange Program FAQ