Which term describes a biological agent such as bacteria, virus, or parasite that causes disease in a host?

Which term describes a biological agent such as bacteria, virus, or parasite that causes disease in a host?

• A. Pathogen
• B. Germ
• C. Microbe
• D. Contaminant

Answer: (A)

Biological agents that cause disease are called pathogens. The term specifically names any organism or particle that can invade a host and trigger illness, including bacteria, viruses, parasites, and fungi. A germ is an informal, broad label for microorganisms and doesn’t always imply disease. A microbe is even broader, covering all microscopic organisms—many are harmless or beneficial. A contaminant refers to an unwanted substance in a context like food or air, not necessarily tied to disease-causing ability. So, the word that best describes a disease-causing biological agent is pathogen.

Biological agents that cause disease are called pathogens. The term specifically names any organism or particle that can invade a host and trigger illness, including bacteria, viruses, parasites, and fungi. A germ is an informal, broad label for microorganisms and doesn’t always imply disease. A microbe is even broader, covering all microscopic organisms—many are harmless or beneficial. A contaminant refers to an unwanted substance in a context like food or air, not necessarily tied to disease-causing ability. So, the word that best describes a disease-causing biological agent is pathogen.