Final answer:
The duration from the onset of signs and symptoms of diseases until the resolution of symptoms or death is called the period of decline.
Step-by-step explanation:
The duration from the onset of signs and symptoms of diseases until the resolution of symptoms or death is called the period of decline. This period occurs after the period of illness, when the number of pathogen particles begins to decrease and the signs and symptoms of illness begin to decline. During the decline period, patients may become susceptible to developing secondary infections because their immune systems are still weakened.