A disease is an abnormal state of an organization which deteriorates its health or its functions.
At the human being, the term disease is often used more largely to refer to any condition causing discomfort, body Dysfonctionnement, distresses, distress, problems social or even the death at the person concerned, or of the similar problems at the people in contact with it.
In this broader direction, the term included sometimes the Wound S, Handicap S, disorders, Syndrome S, Infection S, Symptom S isolated, behaviors abnormal, and atypical variations of the structure of the bodies and body functions, while in other contexts those can be regarded as categories with whole share.
Health and the disease are integral parts of the life, the process biological and the interactions with social environment and environmental. Generally, the disease is defined as an entity opposed to the health, of which the negative effect is with a deterioration or a desharmonisation of a system on an unspecified level (molecular, body, mental, emotional, spiritual, etc) of the physiological or morphological state regarded as normal, balanced or harmonious. One can speak about setting at fault of the Homéostasie.
The diseases which affect the botanical plants and other subjects, relate to phytopathology. Pathologies which affect the animals are veterinary field of science. The human disease is the core founder of medicine, most of medical knowledge being directed towards the disease and its solutions.
To classify a certain state as a disease is a social fact of evaluation, and can change the social status of the person concerned. Certain states known under the name of cultural syndromes are recognized like diseases only in certain cultures. Sometimes the categorization of a state as a disease is discussed within the same company.
Causes of diseasesThere exist many different factors being able to involve the appearance of a disease.
These factors can be as well intrinsic as extrinsic at the organization concerned with the disease.
One can quote in intrinsic examples of factors the genetic affections or nutritional deficiencies. On the other hand, an environmental exposure, such as passive smoking, is an external factor.
The presence of an intrinsic factor does not exclude that from an extrinsic factor, and conversely. Thus from many diseases result from a combination of intrinsic and extrinsic factors. For some others, no cause or groups causes could not be identified.
The factors can be distributed in the following categories:
- social Factors
- psychological Factors
- chemical Factors
- biological Factors
It is the case of the biochemical causes of diseases which can be regarded as a spectrum where with the one of the ends the disease is caused exclusively by genetic factors (for example repetitions CAG in the Huntington gene which causes the disease of Huntington) and with the other caused entirely by environmental factors.
Environmental factors included toxic chemicals (for example acetaldehydes in the cigarette smoke and dioxanes slackened during the use of Orange agent) and infectious agents (for example viruses of chicken pox or the polio). Between these two extremes, environmental genes and factors interact to cause the disease as it is the case for the inflammatory disease called disease of Crohn where the genes NOD2/CARD15 and the intestinal flora play a part. The absence of genetic factor or environmental in this case with for result the absence of manifestation of the disease. The postulates of Koch can be used to determine if a disease is caused by an infectious agent.
Study of the genetic factorsTo determine if a disease is caused by a genetic factor, the researchers study the presence of the disease in the family family tree. That provides qualitative information in connection with the disease, i.e. how she is inherited.
A traditional example of this method of research is the heritage of the hemophilia in the British royal family. More recently this method was used to identify the gene Apoliprotéine E (ApoE) like a gene likely to be related to the disease of Alzheimer, although the certain shapes of this gene (ApoE2) is less likely.
To determine up to which point a disease is caused by genetic factors, i.e. to obtain quantitative information, studies on twins are carried out. The twins monozygotes are genetically identical whereas the twins dizygotes are only genetically similar. Moreover of the twins, who they are monozygotes or dizygotes, often share a similar environment. Thus by comparing the incidence of the disease (named rate of agreement) among twins monozygotes with the incidence of the disease among twins dizygotes, the contribution of each gene to the disease can be given.
The suspect genes can be identified thanks to several methods. One of them is the search for change of a model organization (for example the organizations Mus musculus , Drosophila melanogaster , Caenhorhabditis elegans , Brachydanio rerio and Xenopus tropicalis ) which have a phenotype similar to the studied disease. Another approach is the search for gene segregation or the use of genetic Marqueurs (for example the S.N.P. (individual nucleotide polymorphism) and Expressed sequence tag).
Dependant conceptsThe medical use distinguishes sometimes a disease , which has a known specific cause, called its etiology, of a syndrome, which is a number of clinical signs and possibly paraclinic or symptoms which appear together. However, much of state having been identified continue to be called syndromes. Moreover, many states of unknown causes are called diseases in many contexts.
Social significanceThe identification of a state like a disease, rather than like a simple variation in the human structure or functions, can have social and economic implications significant.
The disease can sometimes involve the social exclusion of the touched people. An example is the exclusion of the Lépreux, current in Europe since the Middle Ages, and their regrouping in establishments called Léproseries with an aim of limiting the propagation of the disease by contagion.
The fear of the disease was and is still a very widespread social phenomenon, although all the diseases, in particular most benign, do not have this kind of reflect social.
A state can be regarded as a disease in certain cultures or at certain times and not in others. The hyperactivity and obesity are for example states increasingly considered as diseases in the Western countries but were not thus considered still a few decades ago and are still not it in certain countries. On the contrary, the number of people considering homosexuality as a disease in these same countries goes decreasing.
Transmission of the diseaseCertain diseases are contagious or infectious, as it is the case for example of the Influenza. The infectious illness can be transmitted by a great number of mechanisms, including the expulsion of particles in the air at the time of a sneeze or a cough, the Fomite S, the bites and insect bites or other animals vectors carrying the disease, and the absorption of water or contaminated food. There exist also sexually transmitted diseases.
In certain countries, most dangerous of them, from the point of view of the epidemic risk, are notifiable diseases, i.e. which they must be declared with the authorities as soon as they are diagnosed by the doctor or the veterinary surgeon.
ClassificationsThe Nosologie is interested in systematic classification of the diseases.
From the medical Diagnostic established thanks to the analysis of the Symptôme S or with medical Analyzes of biological samples and systems of medical imagery (Radiographie, Scanner, etc), the diseases identified by names, more and more is standardized and located by codes CIM (international Classification of the diseases), which allows a better treatment of the statistics useful for epidemiology and less risks of error in the use of the Médicament S.
Other usesBy extension, one can associate the disease of the nonbiological entities. It is usual to hear the terms sick company or sick company for example.
- List of current diseases
- Infectious illness
- hereditary Genetic diseases
- infantile Diseases
- psychosomatic Mental diseases
- Diseases opportunist
- Rare diseases, known as orphan
- Sexually transmitted diseases (MST)
- transmissible Infection sexually (ITS)
- Viral diseases
- neurodégénérative Disease
- Handicap S
- Traumatism (Fracture S, Wound S, Burn S…)
- Health, Hygiene,
- Epidemic, Pandemia, pandemic Risk
- palliative Care
- Turbid functional
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