DiseaseFromWikipedia,thefreeencyclopediaThisisthelatestacceptedrevision,reviewedon15September2021.JumptonavigationJumptosearchAbnormalconditionthatnegativelyaffectsanorganismForotheruses,seeDisease(disambiguation)."Maladies"redirectshere.Forthe2012film,seeMaladies(film)."Ailment"redirectshere.ItisnottobeconfusedwithAliment.ScanningelectronmicrographofMycobacteriumtuberculosis,abacteriumthatcausestuberculosisAdiseaseisaparticularabnormalconditionthatnegativelyaffectsthestructureorfunctionofallorpartofanorganism,andthatisnotduetoanyimmediateexternalinjury.[1][2]Diseasesareoftenknowntobemedicalconditionsthatareassociatedwithspecificsignsandsymptoms.Adiseasemaybecausedbyexternalfactorssuchaspathogensorbyinternaldysfunctions.Forexample,internaldysfunctionsoftheimmunesystemcanproduceavarietyofdifferentdiseases,includingvariousformsofimmunodeficiency,hypersensitivity,allergiesandautoimmunedisorders.Inhumans,diseaseisoftenusedmorebroadlytorefertoanyconditionthatcausespain,dysfunction,distress,socialproblems,ordeathtothepersonafflicted,orsimilarproblemsforthoseincontactwiththeperson.Inthisbroadersense,itsometimesincludesinjuries,disabilities,disorders,syndromes,infections,isolatedsymptoms,deviantbehaviors,andatypicalvariationsofstructureandfunction,whileinothercontextsandforotherpurposesthesemaybeconsidereddistinguishablecategories.Diseasescanaffectpeoplenotonlyphysically,butalsomentally,ascontractingandlivingwithadiseasecanaltertheaffectedperson'sperspectiveonlife.Deathduetodiseaseiscalleddeathbynaturalcauses.Therearefourmaintypesofdisease:infectiousdiseases,deficiencydiseases,hereditarydiseases(includingbothgeneticdiseasesandnon-genetichereditarydiseases),andphysiologicaldiseases.Diseasescanalsobeclassifiedinotherways,suchascommunicableversusnon-communicablediseases.Thedeadliestdiseasesinhumansarecoronaryarterydisease(bloodflowobstruction),followedbycerebrovasculardiseaseandlowerrespiratoryinfections.[3]Indevelopedcountries,thediseasesthatcausethemostsicknessoverallareneur