STAGE 1: INCUBATION PERIOD

This refers to the time elapsed between exposure to a pathogenic organism, and from when symptoms and signs are first apparent.

STAGE 2: PRODROMAL PERIOD

In this phase, the numbers of the infectious agents start increasing and the immune system starts reacting to them. It is characterized by early symptoms that might indicate the start of a disease before specific symptoms occur.

STAGE 3: ACUTE PERIOD

This stage is characterized by active replication or multiplication of the pathogen and its numbers peak exponentially, quite often in a very short period of time.

STAGE 4: CONVALESCENCE PERIOD

The patient recovers gradually and returns to normal, but may continue to be a source of infection even if feeling better. In this sense, recovery can be considered a synonymous term.