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." An infection occurs when harmful microorganisms such as bacteria, viruses, fungi, or parasites enter the body, multiply, and cause disease. This scenario allows pathogens to disrupt normal bodily functions and provoke immune responses, leading to various symptoms depending on the type of pathogen and the area affected.

In contrast, other terms listed refer to different concepts. Infestation generally refers to the presence of larger parasites, such as insects or worms, which can overrun an organism or its environment. Contamination indicates the presence of unwanted substances, which may not necessarily cause disease; it may refer to the introduction of pathogens into a sterile environment without actual invasion. Inflammation is a biological response to harmful stimuli, such as pathogens or irritants, but it is a reaction to infection rather than the invasion itself. Understanding these differences is crucial for identifying and addressing health issues properly.