What are the different biosafety levels?

Biosafety Level 1 (BSL-1)

Involves work with agents that pose minimal threat to lab workers and the environment.

These microorganisms are not known to consistently cause disease in healthy adult humans.

Standard microbiological practices are sufficient; no special containment equipment is needed.

Examples: Bacillus subtilis, Escherichia coli K-12, non-pathogenic strains of yeast.

Labs may be open to the general building; handwashing and surface decontamination are the main safeguards.

Biosafety Level 2 (BSL-2)

Handles agents that pose moderate hazards to personnel and the environment.

Pathogens may cause human disease but are generally treatable and preventable.

Requires limited access, use of personal protective equipment (PPE), and biosafety cabinets for aerosol-generating procedures.

Examples: Staphylococcus aureus, Salmonella spp., Hepatitis B virus, HIV, Toxoplasma gondii.

Emphasis is placed on biological safety cabinets and autoclaving of waste.

Biosafety Level 3 (BSL-3)

Used for work with indigenous or exotic agents that may cause serious or potentially lethal disease through inhalation.

Requires controlled access, directional airflow with air not recirculated, and respiratory protection.

All manipulations involving infectious materials must be conducted within a certified Class II or Class III biological safety cabinet.

Examples: Mycobacterium tuberculosis, Yersinia pestis, Coxiella burnetii, SARS-CoV-2.

Labs must have special engineering features including sealed windows and walls, and a dedicated exhaust system.

Biosafety Level 4 (BSL-4)

Reserved for work with highly dangerous and exotic agents that pose a high risk of life-threatening disease, for which there are no available vaccines or treatments.

Personnel must wear full-body, air-supplied, positive-pressure suits.

The lab must be completely isolated with dedicated supply and exhaust systems, chemical showers for decontamination, and rigorous waste management protocols.

Examples: Ebola virus, Marburg virus, Lassa virus, Crimean-Congo hemorrhagic fever virus.

These facilities are extremely rare and highly secure, often associated with national or international reference laboratories.