In a fundamental sense, therefore, disease represents the consequences of a breakdown of the homeostatic control mechanisms. In some instances, the affected mechanisms are clearly indicated, but in most cases, a complex of mechanisms is disturbed, initially or sequentially, and a precise definition of the pathogenesis of the ensuing disease is elusive. There are several measures used to quantify the burden imposed by diseases and conditions on people. The years of potential life lost is a simple estimate of the number of years that a person’s life was shortened due to a disease. For example, if a person dies at the age of 65 from a disease, and would probably have lived until age 80 without that disease, then that disease has caused a loss of 15 years of potential life. YPLL measurements do not account for how disabled a person is before dying, so the measurement treats a person who dies suddenly and a person who died at the same age after decades of illness as equivalent.

Second, there must be a feasible intervention that, when targeted to people with the disease, effectively reduces the likelihood of developing the disease. Third, the benefits of intervening in disease must outweigh the harms in the population. When the cause of a disease is poorly understood, societies tend to mythologize the disease or use it as a metaphor or symbol of whatever that culture considers evil.

Epidemiology is considered a cornerstone methodology of public health research and is highly regarded in evidence-based medicine for identifying risk factors for diseases. Epidemiologists also study the interaction of diseases in a population, a condition known as a syndemic. Epidemiologists rely on a number of other scientific disciplines such as biology, biostatistics, Geographic Information Science, and social science disciplines.

Epidemiology can help identify causes as well as guide prevention efforts. Only some diseases such as influenza are contagious and commonly believed infectious. The microorganisms that cause these diseases are known as pathogens and include varieties of bacteria, viruses, protozoa, and fungi.

This usage appears in statements that describe a patient as being in critical condition, for example. In humans, the disease is often used more broadly to refer to any condition that causes pain, dysfunction, distress, social problems, or death to the person affected, or similar problems for those in contact with the person. Diseases can affect people not only physically, but also mentally, as contracting and living with a disease can alter the affected person’s perspective on life. Preventive healthcare is a way to avoid an injury, sickness, or disease in the first place.

Without an agreed-on definition, different researchers may report different numbers of cases and characteristics of the disease. Treatment for medical emergencies must be provided promptly, often through an emergency department or, in less critical situations, through an urgent care facility. Alternatively, diseases may be classified according to the organ system involved, though this is often complicated since many diseases affect more than one organ. The study of disease is called pathology, which includes the study of etiology, or cause. Mayo Clinic is a nonprofit organization and proceeds from Web advertising help support our mission.

Britannica Explains In these videos, Britannica explains a variety of topics and answers frequently asked questions. Disease burden is the impact of a health problem in an area measured by financial cost, mortality, morbidity, or other indicators. In studying diseases, epidemiology faces the challenge of defining them. Especially for poorly understood diseases, different groups might use significantly different definitions.

Sudden Cardiac Death in AthletesHow familiar are you with the risk factors for and common causes of sudden cardiac death in male and female athletes? We strive to fundamentally transform what it means to live with a disease or condition. Prion diseases are transmissible, untreatable, and fatal brain diseases of mammals. Their cause is highly unusual, and prion disease symptoms reflect the brain being destroyed.