What is defined as an organism that causes disease?

The term that describes an organism responsible for causing disease is "pathogen." Pathogens include various types of organisms, such as bacteria, viruses, fungi, and protozoa, that can invade other living beings and lead to illness or disease. They are capable of triggering harmful responses from the host's immune system, resulting in symptoms and health issues.

Understanding pathogens is crucial for effective disease management, and they play a significant role in both human health and agriculture. Differentiating them from other terms is essential: parasites live on or in a host and typically benefit at the host's expense, while vectors are organisms that transmit pathogens from one host to another. A host, on the other hand, signifies the organism that harbors a pathogen. Recognizing these distinctions reinforces the definition of a pathogen as the primary agent responsible for disease causation.