Stanford University follows the categorizing of infectious agents into levels as described in Biosafety in Microbiological and Biomedical Laboratories (BMBL), 5th edition, written and published by the Centers for Disease Control (CDC) and NIH. The BMBL describes combinations of microbiological practices, laboratory facilities, and safety equipment in combination with four biosafety levels for various agents infectious to humans. The descriptions of biosafety levels (BSL) 1 – 4 parallel those in the NIH Guidelines for research involving recombinant DNA. Biosafety levels are also described for infectious disease activities that involve laboratory animals. It is important to note that the guidelines presented in the BMBL are considered minimal for containment, and will be customized as needed.
The BSL categories are divided up by risk of disease combined with availability of preventive and therapeutic treatments. The four groups are shown in Table 1. For the list of agents and their categories, see Biosafety Levels for Biological Agents or go to the ABSA Website.
Table 1. Basis for the classification of biohazardous agents by biosafety level
| BSL1 |
Agents that are not associated with disease in healthy adult humans |
| BSL2 |
Agents that are associated with human disease which is rarely serious and for which preventive or therapeutic interventions are often available |
| BSL3 |
Agents that are associated with serious or lethal human disease for which preventive or therapeutic interventions may be available (high individual risk but low community risk) |
| BSL4 |
Agents that are likely to cause serious or lethal human disease for which preventive or therapeutic interventions are not usually available (high individual risk and high community risk) |
