Disease: Difference between revisions
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A '''disease''' is an abnormal condition of an organism that impairs bodily functions,<ref>[http://wordnet.princeton.edu/perl/webwn?s=disease WordNet Search - 3.0<!-- Bot generated title -->]</ref> associated with specific [[symptom]]s and [[Medical sign|sign]]s.<ref>[http://www.emedicine.com/asp/dictionary.asp?keyword=disease eMedicine/Stedman Medical Dictionary Lookup!<!-- Bot generated title -->]</ref><ref>{{Dorlands|d_22|12300762}}</ref> |
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In human beings,"disease" is often used more broadly to refer to any condition that causes [[Pain and nociception|discomfort]], [[dysfunction]], [[distress]], [[social problems]], and/or [[death]] to the person afflicted, or similar problems for those in contact with the person. In this broader sense, it sometimes includes [[injury|injuries]], [[disability|disabilities]], [[Disorder (medicine)|disorder]]s, [[syndrome]]s, [[infection]]s, isolated [[symptom]]s, deviant [[behavior]]s, and atypical [[human variability|variation]]s of structure and function, while in other contexts and for other purposes these may be considered distinguishable categories.{{Fact|date=November 2007}} |
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Classifying a condition as a disease is a social act of valuation, and may change the social status of the person with the condition (the [[patient]]). Some conditions (known as [[culture-bound syndrome]]s) are only recognized as diseases within a particular culture. Sometimes the categorization of a condition as a disease is controversial within the [[culture]]. |
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==Causes of disease== |
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Many different factors intrinsic or extrinsic to a person (or plant or animal) can cause disease. Examples of intrinsic factors are [[Genetic disorder|genetic defects]] or nutritional deficiencies. An environmental exposure, such as [[second-hand smoke]] is an example of an extrinsic factor. Many diseases result from a combination of intrinsic and extrinsic factors. For many diseases, many cause or set of causes has been identified. |
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There are many different factors that can cause disease. These can be broadly categorized into the following categories such as [[social]], [[psychological]], [[chemical]], and [[biological]]. Some factors may fall into more than one category. Biochemical causes of disease can be considered as a [[spectrum]] where at one extreme disease is caused entirely by genetic factors (e.g. [[CAG repeats]] in the [[Huntingtin protein]] gene that causes [[Huntington's Disease]]) and at the other extreme is caused entirely by environmental factors. Environmental factors include [[toxic]] chemicals (e.g. [[acetaldehyde]] in [[cigarette]] smoke and [[dioxins]] released from the breakdown of [[Agent Orange]]) and infectious agents (e.g. [[smallpox]] [[virus]] and [[poliovirus]]). In between these extremes genes (e.g. [[NOD2]]/[[CARD15]]) and environmental factors (e.g. [[Gut microbiota]]) interact to cause disease, as seen for example in the [[inflammatory bowel disease]] [[Crohn's Disease]] (Fig 1, right).[[Image:Causes of disease Rowan April 2007.jpg|thumb|right|Figure 1. The biochemical basis of disease. Some diseases, not illustrated here, also have a social and psychological basis.]] Absence of the genetic or environmental factors in this case results in disease not being manifest. [[Koch's postulates]] can be used to determine whether a disease is caused by an infectious agent. |
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To determine whether a disease is caused by genetic factors, researchers study the pattern inheritance of the disease in families. This provides [[qualitative]] information about the disease (how it is inherited). A classic example of this method of research is inheritance of [[hemophilia]] in the [[British Royal Family]]. More recently this research has been used to identify the [[Apoliprotein E]] (ApoE) gene as a susceptibility gene for Alzheimer's Disease, though some forms of this gene - [[ApoE2]] - are associated with a lower susceptibility. To determine to what extent a disease is caused by genetic factors ([[quantitative]] information), [[twin studies]] are used. [[Monozygotic twins]] are genetically identical and likely share a similar environment whereas [[dizygotic twins]] are genetically similar and likely share a similar environment. Thus by comparing the [[incidence (epidemiology)|incidence]] of disease (termed [[concordance rate]]) in monozygotic twins with the incidence of disease in dizygotic twins, the extent to which genes contribute to disease can be determined. Candidate disease genes can be identified using a number of methods. One is to look for [[mutants]] of a [[model organism]] (e.g. the organisms ''Mus musculus'',''Drosophila melanogaster'', ''Caenhorhabditis elegans'',''Brachydanio rerio'' and ''Xenopus tropicalis'') that have a similar [[phenotype]] to the disease being studied. Another approach is to look for [[segregation]] of genes or genetic markers (e.g. [[single nucleotide polymorphism]] or [[expressed sequence tag]]) (Fig. 2). |
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[[Image:Disease gene segregation.jpg|thumb|right|Figure 2. Genetic markers help locate a disease gene]]A large number of SNPs spaced throughout the [[genome]] have been identified recently in a large project called the [[HapMap]] project<ref>{{cite journal|author=McVean G, Spencer CC, Chaix R|journal=PLoS Genet|title=Perspectives on human genetic variation from the hapmap project|volume=1|issue=4|pages=e54|year=2005|pmid=16254603}}This review is free of charge</ref><ref>{{cite journal|author=Skelding K.A., Gerhard GS, Simari RD, Holmes DR Jr|journal=Nat Clin Pract Cardiovasc Med|title=The effect of HapMap on cardiovascular research and clinical practice|volume=4|issue=3|pages=136-142|year=2007|pmid=17330125}}</ref>). The usefulness of the [[HapMap]] project and [[SNP typing]] and their relevance to society was covered in the [[27 October]] [[2005]] issue of the leading international science [[journal]] [[Nature (journal)]].<!-- Image with unknown copyright status removed: [[Image:Nature HapMap Issue 27th October 2005.jpg|thumb|left|Figure 3. A special issue of the leading science journal 'Nature' focusing on results from the [[HapMap]] project]] --> |
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A large number of genes have been identified that contribute to human disease. These are available from the US [[National Library of Medicine]], which has an impressive range of biological science resources available for free online. Amongst these resources is Online [[Mendelian Inheritance]] in Man - [[OMIM]] that provides a very, very comprehensive list of all known human gene mutations associated with, and likely contributing to, disease. Each article at [[OMIM]] is regularly updated to include the latest scientific research. Additionally, each article provides a detailed history of the research on a given disease gene, with links to the research articles. This resource is highly valuable and is used by the world's top science researchers. |
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==Transmission of disease== |
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{{Main|Transmission (medicine)}} |
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Some diseases such as [[influenza]] are contagious and [[Infectious disease|infectious]]. Infectious diseases can be transmitted by any of a variety of mechanisms, including [[aerosols]] produced by [[cough]]s and [[sneeze]]s, by bites of insects or other carriers of the disease, and from contaminated water or food (possibly by [[faeces]]), etc. Also, there are [[sexually transmitted diseases]]. When [[micro-organisms]] that cannot be spread from person to person might play a role, some diseases can be prevented with proper [[nutrition]]. Other diseases such as [[cancer]] and [[heart disease]] are not considered to be caused by [[infection]]. The same is true of mental diseases. |
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==Social significance of disease== |
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Living with disease can be very difficult. The identification of a condition as a disease, rather than as simply a variation of human structure or function, can have significant social or economic implications. The controversial recognitions as diseases of [[post-traumatic stress disorder]], also known as "[[Soldier's heart]]," "[[shell shock]]," and "combat fatigue;" [[repetitive motion injury]] or [[repetitive stress injury]] (RSI); and [[Gulf War syndrome]] has had a number of positive and negative effects on the financial and other responsibilities of governments, corporations and institutions towards individuals, as well as on the individuals themselves. The social implication of viewing [[senescence|aging]] as a disease could be profound, though this classification is not yet widespread. |
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A condition may be considered to be a disease in some cultures or eras but not in others. [[Oppositional-defiant disorder]]{{Fact|date=October 2007}}, [[attention-deficit hyperactivity disorder]]{{Fact|date=October 2007}}, and, increasingly, [[obesity]]{{Fact|date=October 2007}}, are conditions considered to be diseases in the United States and Canada today, but were not so-considered decades ago and are not so-considered in some other countries{{Views needing attribution|date=October 2007}}. [[Leprosy|Lepers]] were a group of afflicted individuals who were historically shunned and the term "leper" still evokes social [[stigma]]. Fear of disease can still be a widespread social phenomena, though not all diseases evoke extreme social stigma. |
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Sickness confers the social legitimization of certain benefits, such as illness benefits, work avoidance, and being looked after by others. In return, there is an obligation on the sick person to seek treatment and work to become well once more. As a comparison, consider [[pregnancy]], which is not a state interpreted as disease or sickness by the individual. On the other hand, it is considered by the medical community as a condition requiring medical care and by society at large as a condition requiring one's staying at home from work. |
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==Global burden of disease== |
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{{main|Global burden of disease}} |
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This chart, compiled in 2002 from the [[global burden of disease]] study performed by the [[World Health Organization]] shows an overview of the impact of various classifications of disease, segregated by regions with low and high mortality: |
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[[Image:GlobalBurdenOfDisease2002.PNG]] |
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==See also== |
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<div style="-moz-column-count:3; column-count:3;"> |
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* [[Disease management (health)]] |
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* [[Epidemic]] |
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* [[Foodborne illness]] |
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* [[Globalization and disease]] |
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* [[Healthcare]] |
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* [[List of diseases]] |
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* [[List of ICD-9 codes]] |
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* [[List of ICD-10 codes]] |
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* [[Local disease]] |
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* [[Localized disease]] |
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* [[Syndemic]] |
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* [[Systemic disease]] |
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* [[Ten Threats]] |
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* [[Transmission (medicine)|Disease transmission]] |
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* [[Waterborne diseases]] |
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</div> |
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==References== |
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{{reflist}} |
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==External links== |
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{{Wiktionary|disease}} |
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*[http://www.nlm.nih.gov/medlineplus/healthtopics.html Health Topics], [[MedlinePlus]] descriptions of most diseases, with access to current research articles. |
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*[http://www.ncbi.nlm.nih.gov/omim/ OMIM] The best web resource for information on genes that cause disease at [[Online Mendelian Inheritance in Man]] |
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*[http://www.nlm.gov/ NLM] The most comprehensive database of top quality science information on the web at [[US National Library of Medicine]] |
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*[http://www.cdc.gov/health/default.htm Health Topics A-Z], fact sheets about many common diseases at [[Center for Disease Control]] |
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*[http://www.gluvsnap.com/news/ GluvSnap.com], Latest disease and medical news |
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*[http://www.merck.com/pubs/mmanual/sections.htm The Merck manual] containing detailed description of most diseases |
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{{pathology}} |
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[[Category:Diseases| ]] |
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[[Category:Medical terms]] |
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[[ar:مرض]] |
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[[ast:Enfermedá]] |
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[[zh-min-nan:Pīⁿ]] |
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[[br:Kleñved]] |
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[[bg:Болест]] |
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[[ca:Malaltia]] |
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[[cs:Nemoc]] |
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[[cy:Clefyd]] |
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[[da:Sygdom]] |
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[[de:Krankheit]] |
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[[et:Haigus]] |
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[[es:Enfermedad]] |
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[[eo:Malsano]] |
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[[eu:Gaixotasun]] |
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[[fa:بیماری]] |
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[[fr:Maladie]] |
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[[gl:Doenza]] |
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[[hr:Bolest]] |
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[[io:Morbo]] |
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[[id:Penyakit]] |
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[[ia:Maladia]] |
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[[is:Sjúkdómur]] |
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[[it:Malattia]] |
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[[he:מחלה]] |
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[[kk:Ауру]] |
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[[ku:Nesaxî]] |
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[[la:Morbus]] |
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[[lv:Slimība]] |
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[[lt:Liga]] |
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[[ln:Bokɔnɔ]] |
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[[hu:Betegség]] |
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[[ml:രോഗം]] |
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[[ms:Penyakit]] |
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[[nl:Ziekte]] |
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[[ja:病気]] |
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[[no:Sykdom]] |
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[[nn:Sjukdom]] |
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[[oc:Malautiá]] |
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[[ps:ناروغي]] |
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[[pl:Choroba]] |
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[[pt:Doença]] |
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[[ro:Boală]] |
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[[qu:Unquy]] |
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[[ru:Болезнь]] |
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[[sq:Sëmundja]] |
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[[scn:Affizzioni]] |
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[[simple:Disease]] |
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[[sk:Choroba]] |
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[[sl:Bolezen]] |
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[[sr:Болест]] |
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[[fi:Sairaus]] |
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[[sv:Sjukdom]] |
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[[tl:Karamdaman]] |
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[[ta:நோய்]] |
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[[te:వ్యాధి]] |
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[[th:โรค]] |
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[[tr:Hastalık]] |
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[[uk:Хвороба]] |
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[[ur:مرض]] |
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[[yi:קראנקייט]] |
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[[zh:疾病]] |
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