BSL-4 labs are designed and operated for work with:

BSL-4 labs are designed and operated for work with:

• A. Agents that are normally found in the United States but are unknown pathogens
• B. Agents that are only transmissible by the aerosol route
• C. Well-characterized agents which do not cause disease in healthy humans
• D. Agents that cause high individual risk for life-threatening disease

Answer: (D)

BSL-4 is defined by handling agents that cause high individual risk for life-threatening disease, often with no effective treatments or vaccines. Because these pathogens pose the greatest danger, the containment and safety measures are the most rigorous: a separate building or isolated zone, negative air pressure to keep air from escaping the area, exhaust air filtered through high-efficiency filters, and strict procedures for entry and exit. Workers wear full-body, air-supplied positive-pressure suits, and every item leaving the facility is decontaminated. This combination is what makes BSL-4 appropriate for agents like Ebola and Marburg, where the threat is immediate and severe. The other descriptions don’t fit because they mischaracterize the level of risk or the containment requirements. BSL-4 isn’t defined by pathogens being unknown within the US, nor by being aerosol-only in transmission, nor by being well-characterized and non-disease-causing. The defining feature is the high risk of life-threatening disease and the need for maximum containment to protect both the worker and the public.

BSL-4 is defined by handling agents that cause high individual risk for life-threatening disease, often with no effective treatments or vaccines. Because these pathogens pose the greatest danger, the containment and safety measures are the most rigorous: a separate building or isolated zone, negative air pressure to keep air from escaping the area, exhaust air filtered through high-efficiency filters, and strict procedures for entry and exit. Workers wear full-body, air-supplied positive-pressure suits, and every item leaving the facility is decontaminated. This combination is what makes BSL-4 appropriate for agents like Ebola and Marburg, where the threat is immediate and severe.

The other descriptions don’t fit because they mischaracterize the level of risk or the containment requirements. BSL-4 isn’t defined by pathogens being unknown within the US, nor by being aerosol-only in transmission, nor by being well-characterized and non-disease-causing. The defining feature is the high risk of life-threatening disease and the need for maximum containment to protect both the worker and the public.