Infectious Substances (Division 6.2): A material known or reasonably expected to contain a pathogen. A pathogen is a microorganism (including bacteria, viruses, rickettsiae, parasites, fungi) or other agent, such as a proteinaceous infectious particle (prion), that can cause disease in humans or animals.

Category A: An infectious substance in a form capable of causing permanent disability or life-threatening or fatal disease in otherwise healthy humans or animals that are exposed to it. An exposure occurs when an infectious substance is released outside of its protective packaging, resulting in physical contact with human or animals. Classification should be based on the known medical history or symptoms of the source patient or animal, endemic local conditions, or professional judgment concerning the individual circumstances of the source human or animal. Category A poses a higher degree of risk than Category B.  

Culture: An infectious substance containing a pathogen that is intentionally propagated. Culture does not include a human or animal patient specimen. Cultures may be categorized as A or B depending on the microorganism.