Occurrence of Disease 。Incidence Fraction of a population that contracts a disease during a specific time. 。Prevalence Fraction of a population having a specific disease at a given time. Sporadic disease Disease that occurs occasionally in a population. Endemic disease Disease constantly present in a population. 。Epidemic disease Disease acquired by many hosts in a given area in a short time. 。Pandemic disease Worldwide epidemic. 。Herd immunity Immunity in most of a population
• Incidence Fraction of a population that contracts a disease during a specific time. • Prevalence Fraction of a population having a specific disease at a given time. • Sporadic disease Disease that occurs occasionally in a population. • Endemic disease Disease constantly present in a population. • Epidemic disease Disease acquired by many hosts in a given area in a short time. • Pandemic disease Worldwide epidemic. • Herd immunity Immunity in most of a population. Occurrence of Disease
Severity or Duration of a Disease ·Acute disease Symptoms develop rapidly 。Chronic disease Disease develops slowly ·Subacute disease Symptoms between acute and chronic 。Latent disease Disease with a period of no symptoms when the patient is inactive
• Acute disease Symptoms develop rapidly • Chronic disease Disease develops slowly • Subacute disease Symptoms between acute and chronic • Latent disease Disease with a period of no symptoms when the patient is inactive Severity or Duration of a Disease