What term describes the invasion of body tissues by disease-causing pathogens?

The term that describes the invasion of body tissues by disease-causing pathogens is "infection." This occurs when microorganisms such as bacteria, viruses, fungi, or parasites enter the body, multiply, and cause harm to the host, leading to symptoms of illness. Infections can range from mild to severe, depending on the pathogens involved, the body's immune response, and other factors.

Inflammation refers to the body's natural response to injury or infection, characterized by redness, heat, swelling, and pain, but it does not specifically denote the invasion by pathogens. Contamination generally refers to the presence of harmful substances or pathogens on a surface or in a substance without necessarily implying that they have invaded tissues. Infestation typically describes an invasion of the body by larger parasites, such as fleas or lice, rather than microscopic pathogens. Therefore, infection is the most accurate term for the definition provided.