What term describes an organism capable of causing disease?

The term "pathogen" refers specifically to any microorganism, such as bacteria, viruses, fungi, or parasites, that can cause disease in a host organism. Pathogens are capable of invading the body and interfering with normal bodily functions, leading to various clinical illnesses. This term is widely used in microbiology and health sciences to categorize agents responsible for infectious diseases.

Understanding the role of pathogens is essential in the context of wastewater treatment, as these organisms can be present in wastewater and pose significant health risks if not properly managed. Effective treatment processes must be in place to eliminate or reduce these harmful agents to protect public health and the environment.

The other terms, while relevant in the broader context of health and disease, do not accurately describe organisms that cause diseases. Antibodies are proteins produced by the immune system in response to pathogens, allergens refer to substances that provoke allergic reactions, and infectant is not a commonly used term in microbiology. Therefore, "pathogen" is the most accurate and appropriate choice in this context.