Chain of Infection
Break ANY link in the chain to prevent infection.
The chain of infection describes the 6 elements needed for an infection to spread. Nurses break the chain at every possible point to prevent transmission.
- Infectious agent — the pathogen (bacteria, virus, fungus, parasite)
- Reservoir — where the pathogen lives and multiplies (humans, animals, equipment, water)
- Portal of exit — how the pathogen leaves the reservoir (respiratory tract, blood, skin, GI tract)
- Mode of transmission — how it travels (contact, droplet, airborne, vehicle, vector)
- Portal of entry — how it enters the new host (mucous membranes, broken skin, respiratory tract, urinary tract)
- Susceptible host — someone who can get infected (immunocompromised, elderly, neonates, chronic disease)
The MOST effective way to break the chain of infection is hand hygiene. If a question asks "what is the single most important action to prevent infection?" → the answer is ALWAYS hand hygiene.
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Hand Hygiene
The #1 most important infection prevention measure.
Soap & Water vs Alcohol-Based Hand Rub
- When to usesoap & water
- Hands visibly soiled, after restroom, before eating, C. diff, norovirus. Lather for at least 20 seconds.
- When to usealcohol-based rub
- Hands NOT visibly soiled (routine patient care). Apply and rub all surfaces until dry (~15–20 sec). Does NOT kill C. diff spores or norovirus.
Alcohol-based hand sanitizer does NOT kill C. diff spores. If a question mentions C. diff and asks about hand hygiene → soap and water, NOT hand sanitizer.
Standard Precautions
Used with ALL patients, ALL the time, regardless of diagnosis.
Standard precautions assume that ALL blood, body fluids, secretions, excretions (except sweat), non-intact skin, and mucous membranes may be infectious.
- Hand hygiene — before and after every patient contact
- Gloves — when touching blood, body fluids, mucous membranes, non-intact skin
- Gown — when clothing may be contaminated
- Mask/eye protection — when splashes or sprays are anticipated
- Sharps disposal — directly into sharps container. Do NOT recap, bend, or break needles.
- Respiratory hygiene — cover coughs, tissues in trash
- Safe injection practices — one needle, one syringe, one patient
Sweat is the ONLY body fluid NOT included in standard precautions. Everything else — blood, urine, stool, saliva, wound drainage, CSF, semen, vaginal secretions — is treated as potentially infectious.
Transmission-Based Precautions
ADDED to standard precautions when a specific infection is known or suspected.
- Contact
- Precautions: Gown + gloves upon entering room. Dedicated equipment. Private room or cohort. Diseases: MRSA, VRE, C. diff, scabies, lice, RSV, wound infections, localized herpes zoster.
- Droplet
- Precautions: Surgical mask within 3–6 feet. Private room (door can be open). Patient wears mask during transport. Diseases: Influenza, pertussis, bacterial meningitis, mumps, rubella, strep pharyngitis.
- Airborne
- Precautions: N95 respirator (fit-tested). Negative pressure room (door CLOSED). Patient wears surgical mask during transport. Diseases: TB, measles (rubeola), varicella (chickenpox), disseminated herpes zoster.
Airborne precautions = Measles, Chickenpox (Varicella), TB — "My Chicken Vet." These need N95 + negative pressure room.
Droplets are large and fall within 3–6 feet (surgical mask is enough). Airborne particles are tiny and float for long periods (need N95 + negative pressure). Varicella = airborne. Influenza = droplet.
Medical Asepsis vs Surgical Asepsis
Clean technique vs sterile technique.
- Goal
- Medical (Clean): REDUCE the number of pathogens. Surgical (Sterile): ELIMINATE all microorganisms.
- Examples
- Medical: Hand hygiene, clean gloves, clean dressing changes. Surgical: Sterile gloves, sterile field, catheter insertion, wound irrigation.
- Contamination
- Medical: Items can touch clean surfaces. Surgical: If sterile touches non-sterile → contaminated. Discard.
Sterile Field Rules
- 1-inch border around the edge is considered contaminated
- Never turn your back to a sterile field
- Never reach across a sterile field
- Keep sterile items above waist level
- Moisture contaminates a sterile field (strike-through contamination)
- Only sterile items touch the sterile field
- When in doubt, throw it out — start over
If there is ANY question about whether a sterile field or item has been contaminated, it IS contaminated. Do not second-guess — set up a new sterile field.
PPE — Donning & Doffing
The order matters — putting it on and taking it off correctly prevents self-contamination.
Donning (Putting ON)
Doffing (Taking OFF)
"Gloves go first, mask goes last." Gloves are the dirtiest — get them off first. The mask protects your respiratory tract — keep it on longest.
Restraints
LAST resort — know the alternatives, rules, and documentation.
- LAST resort — try alternatives first: reorientation, bed alarm, sitter, redirection, moving closer to nurses' station
- Physician order required — renewed every 24 hours
- Assess circulation every 1–2 hours — pulses, sensation, skin color, capillary refill
- Remove every 2 hours — for ROM, toileting, nutrition, hydration, skin check
- 2-finger rule — 2 fingers between restraint and skin
- Tie to a non-movable part of the bed frame — never a side rail — using a quick-release knot
- Ensure call light is within reach
- Document: reason, type, time, neurovascular checks, release times, patient response
"What should the nurse do FIRST before applying restraints?" → Try least restrictive alternatives. "Which finding requires removing the restraint?" → Impaired circulation (numbness, tingling, pallor, absent pulses).
Fire Safety — RACE & PASS
Two mnemonics you must memorize.
RACE — Fire Response
PASS — Fire Extinguisher
- O₂ supports combustion — turn off if safe
- Close doors to contain fire and smoke
- Do NOT use elevators
- Ambulatory patients evacuate first → wheelchair → stretcher → bed-bound last
Falls Prevention
Falls are the most common safety incident in healthcare.
Risk Factors
- Age >65, history of falls, altered mental status
- Medications: sedatives, opioids, antihypertensives, diuretics
- Impaired mobility, sensory deficits, urinary urgency
- Environmental hazards (wet floors, clutter, poor lighting)
Interventions
- Bed in lowest position, wheels locked
- Call light within reach at ALL times
- Non-skid footwear, adequate lighting
- Toileting schedule, bed alarm for high-risk patients
- Orient patient to room and call light use
- Remove clutter, secure cords and tubing
- Review medications that increase fall risk
? A patient's chart shows age 78, history of two falls, and current medications include furosemide and lorazepam. What is the priority nursing action?
Frequently Asked Questions
Common student questions on this topic.
What is the difference between standard, contact, droplet, and airborne precautions?
Why is C. diff different from other infections regarding hand hygiene?
What are the steps for proper hand washing?
What is the proper order for donning and doffing PPE?
How can I prevent falls in older adults?
What is the National Patient Safety Goal for patient identification?
Quick-Reference Cheatsheet
Every key point from this guide on a single printable page.
Infection Control & Safety Cheatsheet
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