Chain of Infection Notes

The Chain of Infection

What is an Infection?

  • An infection involves the invasion and proliferation of harmful microorganisms, such as bacteria, viruses, fungi, or parasites, within a host organism’s body.
  • These microorganisms disrupt normal bodily functions, damage tissues, and trigger immune responses, leading to disease.

How Disease Spreads

  • Disease spread requires specific conditions known as the Chain of Infection.
  • The chain of infection is a conceptual model illustrating sequential steps for an infectious agent to spread from one host to another, typically involving six links.

Six Links in the Chain of Infection

  • Infectious Agent
  • Reservoir
  • Portal of Exit
  • Means of Transmission
  • Portal of Entry
  • Susceptible Host
Infectious Agent
  • Any microorganism capable of producing an infection.
    • Examples:
      • Bacteria
      • Viruses
      • Fungi
      • Parasites
Reservoir
  • The place where the causative agent can live.
  • Common reservoirs include:
    • The human body
    • Animals
    • The environment
    • Objects with infectious material (e.g., bedpans, urinals, linens, instruments)
Portal of Exit
  • The way for the causative agent to escape from the reservoir.
  • Pathogens can leave the body through:
    • Urine
    • Feces
    • Saliva
    • Blood
    • Tears
    • Mucous discharge
    • Sexual secretions
    • The nose
    • The mouth
    • The rectum
Means of Transmission
  • Pathogens must be transmitted to another reservoir or host where they can live.
  • Two main ways pathogens are transmitted:
    • Direct Contact:
      • Person-to-person spread (physical or sexual contact).
      • Contact with a body secretion containing the pathogen.
      • Contaminated hands are a common source.
    • Indirect Contact:
      • Transmitted from contaminated substances (food, air, soil, insects, feces, clothing, instruments, and equipment).
      • Touching contaminated equipment and spreading pathogens via hands.
      • Breathing in droplets carrying airborne infections.
      • Receiving bites from insects carrying pathogens.
Portal of Entry
  • The way the agent enters a new reservoir or host.
  • Different portals of entry:
    • Breaks in the skin or mucous membrane
    • Respiratory tract
    • Digestive tract
    • Genitourinary tract
    • Circulatory system
Susceptible Host
  • Individuals who can contract the disease.
  • Humans can often fight off causative agents. However:
    • If body defenses are weak, or
    • If a large number of pathogens invade the body,
    • Then the person can become sick.

Breaking the Chain of Infection

  • Eliminating any part of the chain will stop the spread of disease or infection.

Methods to Break the Chain

These methods align with the links in the chain of infection:

  • Infectious Agent:
    • Diagnosis and treatment
    • Antimicrobial stewardship
    • Cleaning, disinfection, and sterilization
    • Infection prevention policies
    • Pest control
  • Reservoir:
    • Cleaning, disinfection, and sterilization of surfaces and equipment
    • Water treatment
    • Proper soil management
  • Portal of Exit:
    • Control of aerosols and splatter
    • Respiratory etiquette
    • Waste disposal
  • Means of Transmission:
    • Hand hygiene
    • Personal protective equipment (PPE)
    • Food safety
    • Isolation
  • Portal of Entry:
    • Hand hygiene
    • Personal protective equipment (PPE)
    • Catheter and tube management
    • First aid
  • Susceptible Host:
    • Immunizations
    • Treatment of underlying diseases
    • Health insurance to ensure access to care
    • Patient education

Handwashing

  • Handwashing is the single most important thing to do in the hospital, whether you are the patient, the healthcare provider, or a visitor.