Final answer:
A disease affecting the entire body due to under- or overfunctioning is known as a systemic disease, distinct from parasitic, occupational, or contagious diseases.
Step-by-step explanation:
A disease that affects the body as a whole, often due to under- or overfunctioning, is called a systemic disease. This differs from a disease that might be classified as parasitic (caused by parasites like protozoa or worms), occupational (related to one's workplace), or contagious (easily spread from person to person).
Systemic diseases can result from various causes, such as infections that spread throughout the body, as in the case of chickenpox or HIV, or from immune system errors, such as in autoimmune disorders like systemic lupus erythematosus or rheumatoid arthritis.