Under United States law, biological select agents or toxins (BSATs)—or simply select agents for short—are bio-agents which (since 1997) have been declared by the U.S. Department of Health and Human Services (HHS) or by the U.S. Department of Agriculture (USDA) to have the "potential to pose a severe threat to public health and safety". The agents are divided into (1) HHS select agents and toxins affecting humans; (2) USDA select agents and toxins affecting agriculture; and (3) overlap select agents and toxins affecting both.
The U.S. Centers for Disease Control and Prevention (CDC) regulates the laboratories which may possess, use, or transfer select agents within the United States in its Select Agent Program (SAP)—also called the Federal Select Agent Program (FSAP)—since 2001. The SAP was established to satisfy requirements of the USA PATRIOT Act of 2001 and the Public Health Security and Bioterrorism Preparedness and Response Act of 2002, which were enacted in the wake of the September 11, 2001 attacks and the subsequent 2001 anthrax attacks.