What term describes a bacteria, virus, or other microorganism capable of causing disease?

• A. Antigen
• B. Pathogen
• C. Reservoir
• D. Vector

Answer: (B)

A microorganism that can cause disease is called a pathogen. Pathogens include bacteria, viruses, fungi, and parasites, and they have the ability to invade a host, multiply, and disrupt normal body functions, leading to illness. This term specifically identifies the disease-causing potential of the organism itself.

Antigen is a substance that the immune system recognizes and responds to, not necessarily a disease-causing organism. A reservoir is where a pathogen can live and multiply, such as in the environment or on animals, but it isn’t the disease-causing agent itself. A vector is an organism that transmits a pathogen from one host to another, like a mosquito spreading a virus; the vector is a carrier, not the disease-causing organism.