Final answer:
An infection is caused when pathogenic bacteria or viruses enter the body, multiply, and disrupt the body's functions, potentially leading to disease. These infections trigger an immune response and can lead to various symptoms and signs.
Step-by-step explanation:
When a pathogenic bacteria or virus enters the body and multiplies to the point of interfering with the body's normal state, it causes an infection. An infection occurs from the successful colonization of a host by a microorganism, which can lead to disease. Diseases caused by these microorganisms, or pathogens, can result in signs and symptoms that represent a deviation from the normal functioning or structure of the host. Not all infections will lead to disease, but when they do, an immediate inflammatory response is typically triggered to combat the invading pathogen.
Infections can enter through various portals where the skin does not provide protection and can be classified as local, focal, or systemic depending on how they spread in the body. Understanding the signs and symptoms, along with the stages of pathogenesis, which include exposure, adhesion, invasion, infection, and transmission, is essential for diagnosing and treating infectious diseases.