How many biosafety levels are defined by the CDC?

The Centers for Disease Control and Prevention (CDC) defines four biosafety levels, each with specific containment requirements and safety practices designed to protect laboratory personnel, the environment, and the public from exposure to pathogens. These levels, known as Biosafety Level 1 (BSL-1) through Biosafety Level 4 (BSL-4), escalate in terms of complexity and safety measures as the risk associated with the pathogens increases.

Biosafety Level 1 is suitable for work with well-characterized agents not known to cause disease in healthy humans. In contrast, Biosafety Level 4 involves the strictest precautions for handling highly dangerous pathogens that can cause severe or fatal diseases, often with no effective treatment or vaccine available. Each level has specific recommendations for laboratory design, equipment, and operational practices to ensure safety based on the risk presented by the infectious agent.