👉 Britannica's definition of "infection" refers to the invasion and multiplication of microorganisms, such as bacteria, viruses, fungi, or parasites, within a host organism, typically leading to disease. This process begins when these pathogens enter the body through various routes, including ingestion, inhalation, or direct contact. Once inside, they can colonize tissues, evade the immune system, and cause harm by disrupting normal cellular functions or triggering inflammatory responses. The severity of an infection depends on factors like the type of pathogen, the host's immune status, and the site of infection. Treatment often involves antibiotics for bacterial infections, antiviral drugs for viruses, antifungal medications for fungi, or antiparasitic agents for parasites, aiming to eliminate the pathogens or control their spread.
