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Chain of Infection Components

The chain of components has six sections. They include:

  • Microorganisms: Disease producing, also called pathogens
    • Virus, parasite, fungus, bacterium
    • Risk factors: Virulence, pathogenicity, ability to enter host
  • Reservoir/Source: Environment/habitat where a pathogen can live and multiply
    • Environmental surfaces/equipment, body fluids (blood, saliva), urine/fecal material, food/water, soil, skin, respiratory tract
  • Portal of Exit: How the pathogen exits or leaves reservoir
    • Skin to skin, skin to surface, blood, mucous membranes, oral cavity, fecal
    • Other potentially infectious material (OPIM): Seminal fluid, joint fluid, saliva, urine/fecal material, any body fluid contaminated with blood
  • Modes of Transport: How a pathogen moves from reservoir to susceptible host
    • Direct Transmission: Airborne, droplet, contact (e.g., skin), bite, needlestick or other sharps injury
    • Indirect Transmission: Fomites – contaminated equipment or medication (multidose vials, single dose vials), vectors, food, water
  • Portal of Entry: Opening where the pathogen may enter
    • Body openings (e.g., mouth, eyes, urinary tract, respiratory tract), incisions, wounds
  • Susceptible Host: The person at-risk: patient or healthcare worker
    • Factors affecting susceptibility (e.g., age, health, co-morbidities, immune system, nutrition, infective dose, medications)
Chain of Infection graphic