Chain of Infection Components

    • 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

Page last reviewed: April 28, 2022