What term describes a disease-causing microorganism?

• A. Pathogenic
• B. Infectious
• C. Bacteria
• D. Virus

Answer: (A)

The term for a disease-causing microorganism is pathogenic. Pathogenic describes any organism—bacteria, viruses, fungi, or parasites—that has the potential to cause disease in a host by invading tissues, disrupting normal function, or producing toxins. It specifically highlights harm to the host, which is what this question is asking about.

Infectious refers to the ability to spread or cause an infection, which is related but not the same as causing disease. Bacteria and virus are categories of organisms, not descriptors of their disease-causing potential, so they don’t directly answer what term describes a disease-causing microorganism.