Which term describes a biological substance capable of transmitting disease?

• A. Germ
• B. Microorganism
• C. Biological agent
• D. Infectious agent

Answer: (D)

Infection control uses the term infectious agent to describe a biological substance capable of transmitting disease because it specifically captures both the ability to cause infection and the capacity to spread from one host to another. This includes bacteria, viruses, fungi, and parasites that can be transmitted and cause illness. A germ is informal and imprecise, a microorganism is any microscopic life form (not necessarily pathogenic or transmissible), and a biological agent is a broad term that can cover non-infectious substances as well. The infectious agent term aligns with the need to identify organisms that pose a risk of transmission and disease, which is central to risk assessment and containment.