Many people assume that biosafety levels and biological risk groups are synonymous, when in fact there are many factors to consider when designating a biosafety level for a biological agent.
There are four risk group classifications established in the NIH Guidelines and The World Health Organization’s Laboratory Biosafety Manual. Risk Group 1 agents are not associated with disease in healthy adults, Risk Group 2 agents are associated with human disease that is rarely serious and for which preventative or therapeutic interventions are often available, Risk Group 3 agents are associated with serious or lethal human disease for with preventative or therapeutic interventions may be available, and Risk Group 4 agents are likely to cause serious or lethal disease for which preventative or therapeutic interventions are not usually available. Risk Group 3 agents have high individual risk and low community risk, while Risk Group 4 agents have both high individual risk and high community risk.
Very similar to risk groups, there are four biosafety levels established in the CDC/NIH publication Biosafety in Microbiological and Biomedical Laboratories. Biosafety levels prescribe the work practices, engineering controls, personal protective equipment, and facility requirements required for working with biological agents. The risk group classification is only one factor to consider when determining the appropriate biosafety level for a particular agent. Other factors to consider include the mode of transmission, pathogenicity, manipulations that will be conducted, volume, experience of staff, and more. A risk assessment considering all the factors should be conducted by the biosafety officer or other knowledgeable individual in order to assign the appropriate biosafety level. Institutional Biosafety Committees are responsible for reviewing work involving recombinant DNA and assigning the appropriate biosafety level. Local ordinances often require compliance with the NIH Guidelines, which should be referenced for assessing risk and establishing appropriate biosafety levels for all work involving recombinant DNA.
It is important to remember that pre-existing conditions, compromised immunity, medications, pregnancy, etc. may make individuals more susceptible than the general population. In some cases, particular individuals may need to take additional precautions beyond the work practices described for the biosafety level.