What is the general term for disease-causing organisms, including bacteria and viruses?

The term "pathogens" refers to any microorganisms that can cause disease, including bacteria, viruses, fungi, and parasites. This broad definition encompasses various disease-causing agents that may invade and disrupt normal biological functions, leading to illness.

In contrast, allergens are substances that can trigger allergic reactions but do not necessarily cause diseases in the traditional sense—they provoke an immune response in sensitive individuals. Antigens are substances that induce an immune response, including both pathogens and non-pathogenic substances, but the term is more commonly used in specific immunological contexts rather than as a general term for disease-causing organisms. Contaminants typically refer to unwanted substances but are not exclusively associated with causing diseases, making "pathogens" the most accurate and comprehensive term in this context.