Biosafety Program

Office of Research & Engagement

Agent Classification

The principal hazardous characteristics of an agent are: its capability to infect and cause disease in a susceptible human or animal host, its virulence as measured by the severity of disease, and the availability of preventive measures and effective treatments for the disease.

The World Health Organization (WHO) has recommended an agent risk group classification for laboratory use that describes four general risk groups based on these principal characteristics and the route of transmission of the natural disease. The four groups address the risk to both the laboratory worker and the community.

The NIH Guidelines established a comparable classification and assigned human etiological agents into four risk groups on the basis of hazard The descriptions of the WHO and NIH risk group classifications are presented below. They correlate with but do not equate to biosafety levels. A risk assessment will determine the degree of correlation between an agent’s risk group classification and biosafety level.

Risk Group Classification NIH Guidelines for Research Involving Recombinant DNA Molecules 2002 World Health Organization Laboratory Biosafety Manual 3rd Edition 2004
Risk Group 1 Agents which are not associated with disease in healthy adult humans. (No or low individual and community risk) A microorganism that is unlikely to cause human or animal disease.
Risk Group 2 Agents which are associated with human disease which is rarely serious and for which preventative or therapeutic interventions are often available. (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.
Risk Group 3 Agents which are associated with serious or lethal human disease for which preventative or therapeutic interventions may be available (high individual risk but low community risk). (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 preventative measures are available.
Risk Group 4 Agents which are likely to cause serious or lethal human disease for which preventative or therapeutic interventions are not usually available (high individual risk and high community risk). High individual risk; high 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 preventative measures are usually not available.

Summary of Recommended Biosafety Levels for Infectious Agents

BSL Agents Practices Primary Barriers & Safety Equipment Facilities (Secondary Barriers)
1 Not known to consistently cause disease in healthy adults Standard Microbiological Practices None required Open bench and sink required
2 Agents associated with human disease. Routes of transmission include percutaneous injury, ingestion, mucous membrane exposure BSL-1 practices plus: Limited access; Biohazard warning sign; “Sharps” precautions; Biosafety manual defining any needed waste decontamination or medical surveillance policies Primary barriers: Class I or II BSCs or other physical containment devices used for all manipulations of agents that cause splashes or aerosols of infectious materials. PPE: Laboratory coats, gloves, face protection as needed BSL-1 plus: Autoclave available
3 Indigenous or exotic agents with potential for aerosol transmission. Disease may have serious or lethal consequences BSL-2 practice plus: Controlled access; Decontamination of all waste; Decontamination of laboratory clothing before laundering; Baseline serum Primary barriers: Class I or II BSCs or other physical containment devices used for all open manipulations of agents;
PPE: Protective laboratory clothing; gloves; respiratory protection as needed
BSL-2 plus: Physical separation from access corridors; Self-closing, double-door access; Exhaust air not recirculated; Negative airflow into laboratory
4 Dangerous/exotic agents which pose high risk of life-threatening disease; Aerosol-transitted laboratory infections have occurred; or related agents with unknown risk of transmission BSL-3 practices plus: Clothing change before entering; Shower on exit; All material decontaminated on exit from facility Primary barriers: All procedures conducted in Class III BSCs or Class I or II BSCs in combination with full-body, air-supplied, positive pressure personnel suit BSL-3 plus: Separate building or isolated zone; Dedicated supply and exhaust, vacuum, and decontamination systems

Summary of Recommended Biosafety Levels for Activities in which Experimentally or Naturally Infected Vertebrate Animals are Used

ABSL Agents Practices Primary Barriers & Safety Equipment Facilities (Secondary Barriers)
1 Not known to consistently cause disease in healthy adults Standard animal care and management practices, including appropriate medical surveillance programs As required for normal care of each species Standard animal facility: No recirculation of exhaust air; Directional air flow; Recommended Hand washing sink is available
2 Associated with human disease; Hazards: percutaneous exposure, ingestion, mucous membrane exposure ABSL-1 practice plus: Limited access; Biohazard warning signs; “Sharps” precautions; Biosafety manual; Decontamination of all infectious wastes and of animal cages prior to washing ABSL-1 equipment plus primary barriers: Containment equipment appropriate for animal species. PPE: Laboratory coats, gloves, face and respiratory protection as needed ABSL-1 plus: Autoclave available; Hand washing sink available; Mechanical cage washer recommended
3 Indigenous or exotic agents with potential for aerosol transmission. Disease may have serious health effects ABSL-2 practice plus: Controlled access; Decontamination of clothing before; Laundering; Cages decontaminated before bedding removed; Disinfectant foot bath as needed ABSL-2 equipment plus: Containment equipment for housing animals and cage dumping activities. Class I, II or III BSCs available for manipulative procedures (inoculation, necropsy) that may create infectious aerosols. PPEs: Appropriate respiratoryprotection ABSL-2 facility plus: Physical separation from access; Corridors; Self-closing, double-door access; Sealed penetrations; Sealed windows; Autoclave available in facility
4 Dangerous/exotic agents that pose high risk of life threatening disease. Aerosol transmission, or related agents with unknown risk of transmission ABSL-3 practices plus: Entrance through change room where personal clothing is removed and laboratory clothing is put on; shower on exiting. All wastes are decontaminated before removal from the facility. ABSL-3 equipment plus: Maximum containment equipment (i.e., Class III BSC or partial containment equipment in combination with full body, air supplied positive-pressure personnel suit) used for all procedures and activities ABSL-3 facility plus: Separate building or isolated zone; Dedicated supply and exhaust, vacuum and decontamination systems; Other requirements outlined in the text

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