Infectious Substances: Category A and Category B
Infectious substances are biological materials capable of causing disease in humans or animals. The HazMat regulations divide them into two risk categories. Category A infectious substances (UN 2814 — for human pathogens; UN 2900 — for animal pathogens): these are materials capable of causing permanent disability, life-threatening or fatal disease in otherwise healthy humans or animals when exposure occurs during transport. Examples include: Ebola virus, Marburg virus, Lassa fever virus, Smallpox virus, Bacillus anthracis (anthrax). Category A materials require specialized packaging (UN-certified triple packaging: primary container, secondary container with absorbent, outer packaging), a Biohazard label, specific shipping papers stating 'Infectious Substance Affecting Humans' or 'Infectious Substance Affecting Animals,' and delivery through certified carriers with specific training. Category B infectious substances (UN 3373): materials that do not meet Category A criteria but still contain known or suspected infectious material. The risk level is lower — these are materials from clinical, diagnostic, or research settings that may contain pathogens. Packaging: double packaging (primary and secondary with absorbent, outer packaging) labeled with the UN 3373 diamond and 'Biological Substance, Category B.' The packaging mark 'UN 3373' replaces the older 'Diagnostic Specimens' or 'Clinical Specimens' marks. Medical laboratories and hospitals are the primary sources of Category B shipments.