How many different risk groups have been establishes for categorizing pathogen severity and risk assessment starting point?

Risk Groups are classifications that describe the relative hazard posed by infectious agents or toxins in the laboratory. The risk group to which an infectious agent or toxin is assigned is the primary, but not only, consideration used in a biological risk assessment to determine the appropriate biosafety level in which a worker can handle the infectious agent or toxin. Other considerations used in a biological risk assessment include the ability of an infectious agent or toxin to cause disease, the way in which the infectious agent or toxin causes disease, the activities performed in the laboratory, the safety equipment and design elements present in the laboratory, and the health and training of the laboratory worker. Risk group levels do not always correspond to biosafety levels. For example, a specific research project’s biological risk assessment for the use of human immunodeficiency virus (HIV), a Risk Group 3 agent, may correctly determine that HIV can be handled under Biosafety Level 2 conditions. Risk groups are designated from 1 (the lowest risk) to 4 (the highest risk).

A listing of the risk group definitions for many countries, including the US, can be found on the American Biological Safety Association website 

The NIH Guidelines defines the risk groups as:

Risk Group 1 (RG1) - Agents that are not associated with disease in healthy adult humans. This group includes a list of animal viral etiologic agents in common use. These agents represent no or little risk to an individual and no or little risk to the community.

Risk Group 2 (RG2) - Agents that are associated with human disease which is rarely serious and for which preventive or therapeutic interventions are often available. These agents represent a moderate risk to an individual but a low risk to the community.

Risk Group 3 (RG3) - Agents that are associated with serious or lethal human disease for which preventive or therapeutic interventions may be available. These agents represent a high risk to an individual but a low risk to the community.

Risk Group 4 (RG4) - Agents that are likely to cause serious or lethal human disease for which preventive or therapeutic interventions are not usually available. These agents represent a high risk to the individual and a high risk to the community.

The World Health Organization (WHO) defines the risk groups as:

WHO Risk Group 1 (no or low individual and community risk) - A microorganism that is unlikely to cause human disease or animal disease.

WHO Risk Group 2 (moderate individual risk, low community risk) - A pathogen that can cause human or animal disease but is unlikely to be a serious hazard to laboratory workers, the community, livestock or the environment. Laboratory exposures may cause serious infection, but effective treatment and preventative measures are available and the risk of spread of infection is limited.

WHO Risk Group 3 (high individual risk, low community risk) - A pathogen that usually causes serious human or animal disease but does not ordinarily spread from one infected individual to another. Effective treatment and preventive measures are available.

WHO Risk Group 4 (high individual and community risk) - A pathogen that usually causes serious human or animal disease and that can be readily transmitted from one individual to another, directly or indirectly. Effective treatment and preventive measures are not usually available.

For more information, please see:

The NIH Guidelines for Research Involving Recombinant or Synthetic Nucleic Acid Molecules

Biosafety in Biomedical and Microbiological Laboratories

The WHO Laboratory Biosafety Manual 

OIE Terrestrial Manual 2012 

How many risk groups are there?

How many risk groups RG are there?

What are risk group 4 organisms examples?

How many biosafety levels have been created to outline recommended?