Study GuideMicrobiology–The Development of Infectious Disease1.Contributing FactorsInfectious disease develops as acompetition between the parasite (pathogen)and thehost (thebody). If the pathogen successfully overcomes the body’s defenses, the normal state of health isdisturbed anddisease occurs.Whether a microorganism is able to cause disease depends on severalcontributing factors. Thesefactors influence the ability of the pathogen toenter the body, survive, multiply, and causedamage.1.1Portals of EntryFor a pathogen to cause infection, it must first enter the body through aportal of entry.The most common portals of entry are:•Mucous membranes, especially those of the:oRespiratory tractoGastrointestinal tractoUrogenital tractAnother important portal of entry is theskin.•Microorganisms can enter through:oCuts or woundsoHair folliclesWhen pathogens enter the bodybeneath the skin, the route is called theparenteral route.1.2Dose of the PathogenThedoserefers to thenumber of microorganismsrequired to establish an infection.•Some diseases require only asmall numberof organismsPreview Mode
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