Infection is the entry and development of what in the body?

• A. The entry and development/multiplication of an infectious agent in the body.
• B. A harmless immune response.
• C. A genetic mutation.
• D. A non-pathogenic exposure.

Answer: (A)

Infection means an invading microorganism entering the body and multiplying in the tissues. The defining piece is that a living infectious agent establishes itself and reproduces, which can lead to disease or illness depending on the pathogen and the host’s defenses. It’s more than just contact with microbes (exposure) or a harmless immune reaction—the key is that the organism actually invades and grows within the body. Not all infections cause noticeable symptoms, but the growth of the pathogen inside the body is what characterizes infection.