👉 Infection, specifically infection with pathogens like bacteria, viruses, fungi, or parasites, occurs when these microorganisms enter a host's body and begin to multiply or cause disease. This process involves several stages: first, the pathogen must breach physical barriers such as the skin or mucous membranes; then, it must survive the host's immune defenses, often through mechanisms that allow it to evade detection or destroy immune cells. Once inside, the pathogen can adhere to and invade host tissues, multiply, and produce toxins that damage cells and tissues, leading to symptoms of infection. The body's response to infection involves both innate and adaptive immune systems working together to eliminate the pathogen, but if the infection is severe or the host's defenses are compromised, it can result in illness or even life-threatening conditions.
