What is the term for an illness caused by microorganisms that multiply in the body?

The term "infection" specifically refers to the state where microorganisms such as bacteria, viruses, fungi, or parasites invade the body and begin to multiply. This process leads to the body's immune response, which can cause various symptoms of illness, such as fever, inflammation, and pain. Infections can occur in different parts of the body and can be localized or systemic depending on how widely the pathogens spread.

Contamination refers to the presence of unwanted microorganisms on surfaces or items, and it doesn't necessarily imply that they are multiplying or causing disease. Infestation generally pertains to larger parasites or organisms, such as insects, taking up residence in or on the body, leading to different health issues. Inflammation is a physiological response to injury or infection characterized by redness, swelling, heat, and pain, but it does not specifically describe the process of microorganisms multiplying in the body. Thus, infection is the most accurate term for an illness caused by the multiplication of microorganisms.