A disease is any condition which results in the disorder of a structure or function in a living organism that is not due to any external injury. The study of disease is called pathology, which includes the study of cause. Disease is often construed as a medical condition associated with specific symptoms and signs. It may be caused by external factors such as pathogens or by internal dysfunctions, particularly of the immune system, such as an immunodeficiency, or by a hypersensitivity, including allergies and autoimmunity.
Information from a dedicated calibration and validation site has proven invaluable in ensuring the accuracy of satellite altimetry measurements. However, more reliable in situ information can be obtained by an international network being developed within an EU-funded project.