Risk Groups; Biosafety Levels

Risk Groups

Biological agents that are known to infect humans are classified according to Risk Groups (RG), with RG1 as the lowest/least harmful and RG4 as the highest.

Risk Group Definitions
  • RG1 Agents – Are not associated with disease in healthy adult humans or animals.
  • RG2 Agents – Are associated with disease that can cause infection of varying severity; rarely lethal.  Host immune system is usually capable of controlling the infection; preventative or therapeutic interventions are often available.
  • RG3 Agents – Are associated with serious or lethal human disease for which preventative or therapeutic interventions may be available (high individual risk but low community risk).
  • RG4 Agents – Are associated with lethal human disease for which preventative or therapeutic interventions are not usually available (high individual risk and high community risk).
  • The Risk Group Classification System takes the following factors into consideration:
    • Pathogenicity of the organism
    • Mode of transmission and host range
    • Availability of effective preventive measures (e.g., vaccines)
    • Availability of effective treatment (e.g., antibiotics)
    • Other factors

Risk Group Comparisons

Does not cause disease in healthy adults.
Can cause infection of varying severity. Rarely lethal. Can be controlled using standard laboratory practices. Agents associated with moderate to severe disease outcome. Can be lethal. Capable of causing severe disease with lethal outcome.
Availability of Treatment Not applicable. Treatment may be  available or host immune system is capable of controlling the infection. Treatment may not be available. Treatment is generally not available. Experimental treatment regimens possible.
Routes of Transmission Not applicable. Ingestion, through the skin, and via facial mucous membranes. Same as Risk Group 2 plus inhalation. Same as Risk Group 3.
Disease Severity to Individual None in healthy adults. Low to moderate.
Moderate to high.
Higher mortality and morbidity.
Highest mortality rates in this category.
Community Risk Low Low Low to Moderate
Perception risk also very high.
Infections Dose Not applicable Generally high (variable) Lower doses capable of infection
Can be as low as
1 organism
Example Agents Non-conjugative strains of E. coli,  Sacchromyces cerevisiae.
Parasites (i.e. Plasmodium, Trypanosomes, Leishmania)
GI pathogens (Salmonella, Shigella)
Bloodborne Pathogens (HBV, HCV, Borrelia).
Mycobacterium tuberculosis, West Nile Virus, Yellow Fever Virus, Rickettsia rickettsi. Ebola virus, Marburg virus, Sabia virus, Equine Morbillivirus.
Rule of Thumb**
Don’t Drink It!
Never eat, drink or smoke in the laboratory.
Don’t Touch It!
Wear gloves, decontaminate work surfaces, avoid touching your face, make sure wounds are covered, work in a BSC, wear eye protection, work behind a shield.
Don’t Breathe It!
Because of inhalation risk, perform all work inside of a biosafety cabinet. Wear respiratory protection if needed.
Don’t Do It!       
Risk Group 4 agents require significant containment.
Source: National Institutes of Health Centers for Disease Control and Prevention’s “Biosafety in Microbiological and Biomedical Laboratories” (5th Edition).
**Source:  Gwladys Caspar’s Quick Guide.  G. Caspar was formerly the Biosafety Officer at Harvard University.
Risk Groups: Searchable Databases
Biosafety Levels

Biosafety Levels (BSLs) prescribe procedures and levels of containment for the particular microorganism or material (including research involving recombinant or synthetic nucleic acid molecules).  BSLs  are ranked from 1-4, with BSL-1 procedures being suitable for working with the lowest/least harmful biological agents.  They correlate with but do not equate to biosafety risk groups.  A risk assessment will determine the degree of correlation between an agent’s risk group classification and biosafety level.

BIOSAFETY LEVEL 1: Description & Work Practices
  • Suitable for work involving:
    • Well-characterized agents not known to consistently cause disease in immunocompetent adult humans, and that present minimal potential hazard to laboratory personnel and the environment.
    • Transgenic or wild-type laboratory animals (e.g., rodents) that are both:
      • Free of zoonotic diseases.
      • Not infected with, implanted with, or containing RG2 or higher agents or materials.
  • Work is typically conducted on open bench tops using standard microbiological practices.
  • Laboratory personnel must have specific training in the procedures conducted in the laboratory and must be supervised by a scientist with training in microbiology or a related science.
  • Personal health status may impact an individual’s susceptibility to infection, ability to receive immunizations or prophylactic interventions.  Individuals having these conditions should be encouraged to self-identify to the institution’s healthcare provider for appropriate counseling and guidance.
  • Standard Microbiological Practices
    • Wash hands after handling viable materials, after removing gloves, and before leaving the laboratory.
    • Wear pants (or other clothing that covers legs) and close-toed shoes.
    • Lab Coats.  Are generally not necessary.  However, wear lab coat or other protective clothing when handling viable materials; remove protective clothing before leaving lab areas.  All protective clothing must be either disposed of in the laboratory or laundered by the work unit, it should never be taken home.
    • Gloves. Wear gloves whenever contact with microorganisms could be reasonably anticipated and/or whenever skin on hands is not intact – including if a rash is present.  Change gloves when contaminated, glove integrity is compromised/suspect, or when otherwise necessary.
    • Goggles.  Wear chemical splash goggles when conducting procedures that have the potential to create splashes of microorganisms or other hazardous materials.
    • Keep laboratory doors closed; only individuals who are involved with the work are allowed in the area.
    • Mouth pipetting is prohibited; mechanical pipetting devices must be used.
    • Perform all procedures with a focus on minimizing the creation of splashes and/or aerosols.
    • Food, eating, drinking, smoking, handling contact lenses, applying cosmetics, and storing food for human consumption are not permitted in laboratory areas (you don’t even want to be chewing gum in the lab!).
    • Pay attention to hand and mouth hygiene while working in the lab (e.g., do not put a pen in you mouth, or behind your ear).
    • Plants and animals not associated with the work being performed should not be permitted in the laboratory.
    • Sharps.  Follow the policies and procedures on the Sharps Safety page, including:
      • Provide sharps containers within easy reach of work stations.
      • Laboratory supervisors should adopt improved engineering and work practice controls that reduce risk of sharps injuries.
      • Needles must not be bent, sheared, broken, recapped, removed from disposable syringes, or otherwise manipulated by hand before disposal.
      • Broken glassware must not be handled directly.  Instead, it must be removed using a brush and dustpan, tongs, or forceps.  Plastic ware should be substituted for glassware whenever possible.
    • Decontaminate: 
      • Work surfaces after completion of work and after any spill or splash of potentially infectious material with appropriate disinfectant.
      • All cultures, stocks, and other potentially infectious materials before disposal using an effective method.  Materials to be decontaminated outside of the immediate laboratory must be placed in a durable, leak proof container and secured for transport.
      • Follow the appropriate decontamination procedures.
    • A sign incorporating the universal biohazard symbol must be posted at the entrance to the laboratory when infectious agents are present.  The sign must include the name and phone number of the laboratory supervisor or other responsible personnel, and may include the name of the agent(s) in use.

BIOSAFETY LEVEL 2: Description & Work Practices

  • Suitable for work involving agents that pose moderate hazards to personnel and the environment.  It is more restrictive than BSL-1.  It includes all BSL-1 practices plus the following:
    • All persons entering the laboratory must be advised of the potential hazards and meet specific entry/exit requirements.
    • Laboratory personnel have specific training in handling pathogenic agents and are supervised by scientists competent in handling infectious agents and associated procedures.  The laboratory supervisor must ensure that laboratory personnel demonstrate proficiency in standard and special microbiological practices before working with BSL-2 agents.
    • Access to the laboratory is restricted when work is being conducted.
    • Protective Laboratory Coats, gowns, smocks, or uniforms designated for laboratory use must be worn while working with hazardous materials.  Remove protective clothing before leaving the laboratory.  Dispose of protective clothing appropriately, or deposit it for laundering by the institution.  It is recommended that laboratory clothing not be taken home.
    • Gloves must be worn to protect hands from exposure to hazardous materials.  Glove selection should be based on an appropriate risk assessment.  Gloves must not be worn outside the laboratory.  In addition, BSL-2 laboratory workers should:
      • Change gloves when contaminated, glove integrity is compromised, or when otherwise necessary.
      • Remove gloves and wash hands when work with hazardous materials has been completed and before leaving the laboratory.
      • Do not wash or reuse disposable gloves.  Dispose of used gloves with other contaminated laboratory waste.  Hand washing protocols must be rigorously followed.
    • Biosafety Cabinet.  All procedures in which infectious aerosols or splashes may be created are conducted in Biosafety Cabinets or other physical containment equipment.  These may include pipetting, centrifuging, grinding, blending, shaking, mixing, sonicating, opening containers of infectious materials, inoculating animals intranasally, and harvesting infected tissues from animals or eggs.
BIOSAFETY LEVELS: Online Searchable Databases for Various Pathogens

*A Note on the BMBL Agent Summary Statements” – Section VIII of the BMBL provides Agent Summary Statements that describe the hazards, recommended precautions, and levels of containment appropriate for handling specific human and zoonotic pathogens in the laboratory and in facilities that house laboratory vertebrate animals.  Agent Summary Statements are included for agents that meet one or more of the following three criteria: 1) the agent is a proven hazard to laboratory personnel working with infectious materials; 2) the agent has a high potential for causing LAIs even though no documented cases exist; and 3) the agent causes grave disease or presents a significant public health hazard.

Caveat:  No one should conclude that the absence of an Agent Summary Statement for a human pathogen means that the agent is safe to handle at BSL-1, or without a risk assessment to determine the appropriate level of containment.  Laboratory Supervisors should also conduct independent risk assessments before beginning work with an agent or procedure new to the laboratory, even though an agent summary statement is available.