A rare disease has such a low prevalence in a population that a doctor in a busy general practice would not expect to see more than one case a year. Rare diseases, including those of genetic origin, are life-threatening or chronically debilitating diseases which are of such low prevalence that special combined efforts are needed to address them. As a guide, low prevalence is taken as prevalence of less than 5 per 10,000 in the Community  .
Rare diseases will vary from population to population, as a disease that is rare in some populations may be common in another. This is especially true of some genetic and infectious diseases. For example, cystic fibrosis is a rare genetic disease in most parts of Asia but is relatively common in some Eurasian populations. Many infectious diseases, such as tropical diseases, are rare outside a given geographic area.
See also List of common diseases.
List of rare diseases
Rare diseases organizations:
- Eurordis -- European Organization for Rare Diseases
- EUROCAT: European network of population based registries for congenital anomalies .
- List of projects funded by year .
- Key documents .
- DG SANCO Task Force on Rare Diseases; Two day conference on Rare Diseases 2005
- DG RESEARCH, TECHNOLOGICAL DEVELOPMENT AND DEMONSTRATION 6TH FRAMEWORK PROGRAMME (2002-2006): Life sciences, genomics and biotechnology for health .
- Orphanet: database of rare diseases .
- Orphan medicinal products .
- Committee for Orphan Medicinal Products (COMP) of the European Agency for the Evaluation of Medicinal Products (EMEA).
- USA: National Organization for Rare Disorders