The chain of infection
Six interlocked chain links in a closed ring, with the mode-of-transmission link drawn snapped open beside a gloved-hand glyph labeled HAND HYGIENE.
The six links
- Infectious agent — the organism itself: bacterium, virus, fungus, or parasite.
- Reservoir — where it lives and multiplies. A colonized wound, a sink drain, a contaminated humidifier, a person.
- Portal of exit — how it leaves the reservoir: respiratory secretions, stool, blood, drainage.
- Mode of transmission — how it travels: contact, droplet, airborne, common vehicle, or vector.
- Portal of entry — how it gets in. An indwelling urinary catheter is a portal of entry that the nurse installed.
- Susceptible host — the patient whose defenses cannot refuse it. An older adult on corticosteroids is a susceptible host.
The break point
Hand hygiene breaks the transmission link and is the single most effective measure available at the bedside. It is also the link the exam tests most, because it is the only one the nurse controls without an order, without equipment, and without anyone's permission.
Who is susceptible
- Age at either extreme, newborn or older adult
- Immunosuppression from disease, chemotherapy, or corticosteroids
- Malnutrition and low serum protein
- Invasive devices of any kind
- Broken skin, surgical wounds, pressure injuries
- Uncontrolled glycemia
Margin noteyou only need to break one link.
Watch outalcohol-based rub does not kill spore-forming organisms. When a patient has a spore-forming diarrheal illness, or whenever hands are visibly soiled, wash with soap and running water instead.
Takeawayinfection needs all six links, so prevention needs only one.
The chain in depth → BOOK 04 · P3. Hand hygiene indications → BOOK 04 · P7.