Final answer:
When an infection becomes disseminated throughout the body, it is called a systemic infection. Secondary infections can occur after a primary infection, and pathogens enter the body through portals of entry and leave through portals of exit.
Step-by-step explanation:
When an infection becomes disseminated throughout the body, we call it a systemic infection. For example, infection by the varicella-zoster virus typically gains entry through a mucous membrane of the upper respiratory system. It then spreads throughout the body, resulting in the classic red skin lesions associated with chickenpox. Since these lesions are not sites of initial infection, they are signs of a systemic infection.
Secondary infections can occur after the host's defenses are compromised by a primary infection or antibiotic treatment. For example, a primary infection by HIV compromises the immune system, making the patient more susceptible to secondary diseases like oral thrush.
Pathogens enter the body through portals of entry and leave through portals of exit. The stages of pathogenesis include exposure, adhesion, invasion, infection, and transmission.