The average percentage increase per year of the incidence and prevalence of autoimmune diseases worldwide were 19% and 13% respectively.
Incidence is the rate of new (or newly diagnosed) cases of the disease. It is generally reported as the number of new cases occurring within a period of time or as a fraction of the population.
Prevalence is the proportion of disease or risk factor affecting a population (for example, cancer, smoking or seat-belt use). It is arrived at by comparing the number of people found to have the condition with the total number of people studied and is usually expressed as a fraction.