The invasion of the body by a disease-producing organism is called infection.

Here's a breakdown of the key terms:

* Disease-producing organism: These are usually microorganisms like bacteria, viruses, fungi, or parasites. They are also called pathogens.

* Infection: This is the process by which a pathogen enters the body, multiplies, and may cause disease.

* Disease: A disease occurs when the pathogen's presence and activity disrupt the normal functioning of the body.

So, an infection is the entry point for a disease, and disease is the result of the infection.