Which biosafety level is associated with indigenous microorganisms that can cause disease of varying severity in healthy adults?

• A. BSL-1
• B. BSL-3
• C. BSL-4
• D. BSL-2

Answer: (D)

Containment levels match how risky the organism is and what protection is needed. Indigenous microorganisms that can cause disease of varying severity in healthy adults are considered moderate risk, so they’re handled at a BSL-2 level. This means standard laboratory practices plus restricted access, proper training, and the use of PPE such as gloves and lab coats (and eye protection when appropriate). Procedures that could generate aerosols should be performed in a biosafety cabinet when possible, and there are specific rules for handling sharps and disposing of waste.

In contrast, nonpathogenic organisms fall under the simplest level, while higher levels are reserved for agents that are more dangerous or transmissible—so BSL-3 requires more containment for serious or lethal diseases transmitted via aerosols, and BSL-4 is used for the most dangerous pathogens with no proven treatments. Therefore, BSL-2 is the best fit.