Final answer:
An infection develops in the body during the incubation period, which is the stage before symptoms appear. The following stages include the prodromal period, the period of illness, the period of decline, and the period of convalescence.
Step-by-step explanation:
An infection develops in the body before any signs or symptoms appear during its incubation period. This is the first phase in the progression of a disease, which begins after the initial entry of the pathogen into the host. During the incubation period, the pathogen starts to multiply, but the numbers are not yet high enough to provoke noticeable signs or symptoms.
Following the incubation period is the prodromal period, which signifies the onset of non-specific signs and symptoms as the pathogen continues to increase in number. Next, the period of illness occurs, where symptoms are most pronounced. Eventually, the period of decline and period of convalescence follow, signaling a decrease in pathogen levels and a return to health, respectively.