What occurs when disease-causing bacteria or viruses enter the body?

When disease-causing bacteria or viruses enter the body, an infection occurs. An infection happens when these pathogens invade the body, multiply, and begin to disrupt normal bodily functions. This process often triggers the immune system to respond, which can result in symptoms such as inflammation, fever, and fatigue, as the body tries to fight off the invading microorganisms.

Infections can vary in severity and can affect specific regions or systems within the body, depending on the type of pathogen and the individual’s health status. It's important to understand that infections are directly linked to the introduction of these harmful agents into the body, leading to illness.

Other terms, such as allergy, contamination, and infestation, describe different biological or environmental processes and do not specifically refer to the invasion and proliferation of infectious agents in the body. Allergies involve an immune response to non-infectious substances, contamination refers to the presence of harmful substances on surfaces or items, and infestation denotes the invasion of the body by larger parasites, such as worms or insects, rather than microscopic pathogens.