What is a pathogen?

What is a pathogen?

• A. An organism capable of causing disease
• B. A chemical
• C. A symptom of infection
• D. A virus only

Answer: (A)

Pathogen refers to an organism capable of causing disease in a host. This includes bacteria, viruses, fungi, and parasites, all defined by their ability to invade, replicate, and damage host tissues or provoke illness. Not every organism is a pathogen—many are harmless or beneficial. A chemical is not an organism and isn’t an infectious agent, so it isn’t a pathogen. A symptom is the result of disease, not the cause. A virus is a type of pathogen, but pathogens also include bacteria, fungi, and parasites, making the concept broader than viruses alone.

Pathogen refers to an organism capable of causing disease in a host. This includes bacteria, viruses, fungi, and parasites, all defined by their ability to invade, replicate, and damage host tissues or provoke illness. Not every organism is a pathogen—many are harmless or beneficial. A chemical is not an organism and isn’t an infectious agent, so it isn’t a pathogen. A symptom is the result of disease, not the cause. A virus is a type of pathogen, but pathogens also include bacteria, fungi, and parasites, making the concept broader than viruses alone.