Prevalence (number of people living with a disease at a given moment), rather than incidence (number of new diagnoses in a given year), is used to describe the impact of<unk> s. The Global Genes Project estimates some 300 million people worldwide are affected by a<unk> . The European Organization for<unk> s (EURORDIS) estimates that as many as 5,000 to 7,000 distinct<unk> s exist, and as much as 6% to 8% of the population of the European Union is affected by one. Only about 400<unk> s have therapies and about 80% have a genetic component according to<unk>  Genomics Institute.<unk> s can vary in prevalence between populations, so a disease that is<unk>  in some populations may be common in others. This is especially true of genetic diseases and infectious diseases. An example is cystic fibrosis, a genetic disease: it is<unk>  in most parts of Asia but relatively common in Europe and in populations of European descent. In smaller communities, the founder effect can result in a disease that is very<unk>  worldwide being prevalent within the smaller community. Many infectious diseases are prevalent in a given geographic area but<unk>  everywhere else. Other diseases, such as many<unk>  forms of cancer, have no apparent pattern of distribution but are simply<unk> . The classification of other conditions depends in part on the population being studied: All forms of cancer in children are generally considered<unk> , because so few children develop cancer, but the same cancer in adults may be more common. About 40<unk> s have a far higher prevalence in Finland; these are known collectively as Finnish heritage disease. Similarly, there are<unk>  genetic diseases among the Amish religious communities in the US and among ethnically Jewish people.
Rare disease
Progressive disease
Chronic condition
Contagious disease
Biphasic disease
Heterogeneous condition
Precancerous condition
Genetic heterogeneity