Medical Microbiology

TheHistoryofInfectiousDiseases 3

TheHenle–KochPostulates................................

Thepostulatescanbefreelyformulatedasfollows:

&Themicroorganismmustbefoundunderconditionscorrespondingtothe

pathologicalchangesandclinicalcourseofthediseaseinquestion.

&Itmustbepossibletocauseanidentical(human)orsimilar(animal)dis-

easewithpureculturesofthepathogen.

&Thepathogenmustnotoccurwithintheframeworkofotherdiseasesas

an“accidentalparasite.”

Thesepostulatesarestillusedtodaytoconfirmthecauseofaninfectiousdis-

ease.However,thefactthattheseconditionsarenotmetdoesnotnecessarily

excludeacontributiontodiseaseetiologybyapathogenfoundincontext.In

particular,manyinfectionscausedbysubcellularentitiesdonotfulfillthe

postulatesintheirclassicform.

ThePresent.................................................

Thefrequencyanddeadlinessofinfectiousdiseasesthroughoutthousandsof

yearsofhumanhistoryhavekeptthematthefocusofmedicalscience.The

developmentofeffectivepreventiveandtherapeuticmeasuresinrecentdec-

adeshasdiminished,andsometimeseliminatedentirely,thegrimepidemics

ofsmallpox,plague,spottedfever,diphtheria,andothersuchcontagions.To-

daywehavespecificdrugtreatmentsformanyinfectiousdiseases.Asaresult

ofthesedevelopments,theattentionofmedicalresearcherswasdivertedto

otherfields:itseemedwehadtamedtheinfectiousdiseases.Recentyears

haveprovedthisassumptionfalse.Previouslyunknownpathogenscausing

newdiseasesarebeingfoundandfamiliarorganismshavedemonstrated

anabilitytoevolvenewformsandreassertthemselves.Theoriginsofthis

reversalaremanyandcomplex:humanbehaviorhaschanged,particularly

intermsofmobilityandnutrition.Furthercontributoryfactorswerethein-

troductionofinvasiveandaggressivemedicaltherapies,neglectofestab-

lishedmethodsofinfectioncontroland,ofcourse,theabilityofpathogens

tomakefulluseoftheirspecificgeneticvariabilitytoadapttochangingcon-

ditions.Theupshotisthatphysiciansinparticular,aswellasothermedical

professionalsandstaff,urgentlyrequireabasicknowledgeofthepathogens

involvedandthegenesisofinfectiousdiseasesiftheyaretorespondeffec-

tivelytothisdynamisminthefieldofinfectiology.Theaimofthistextbookis

toimparttheseessentialstothem.

Table 1. 1 providesanoverviewofthecausesofhumaninfectiousdiseases.

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Kayser, Medical Microbiology © 2005 Thieme