Overview
Infection control protects patients, health care workers, and the community from the spread of harmful microorganisms. Health care-associated infections cause real harm, yet many are preventable with simple, reliable practices. This lesson covers how infection spreads, the two levels of asepsis, hand hygiene, the precaution systems, and the safe use of protective equipment.
The Chain of Infection
For infection to spread, six links must connect. Break any one link and transmission stops.
| Link | What it is | Example of breaking it |
|---|---|---|
| Infectious agent | The pathogen (bacterium, virus, fungus) | Antibiotics; disinfection |
| Reservoir | Where the agent lives and multiplies | Cleaning surfaces; treating carriers |
| Portal of exit | How it leaves the reservoir | Covering coughs; dressing wounds |
| Mode of transmission | How it travels (contact, droplet, airborne) | Hand hygiene; PPE |
| Portal of entry | How it enters a new host | Aseptic technique; catheter care |
| Susceptible host | A person able to be infected | Vaccination; good nutrition |
Hand hygiene is emphasized because the mode of transmission, especially by hands, is the link nurses can most often break.
Medical vs. Surgical Asepsis
Asepsis means the absence of disease-causing microorganisms. There are two levels:
- Medical asepsis (clean technique) reduces the number and spread of microorganisms — hand hygiene, cleaning surfaces, and using clean gloves. It is used for most routine care.
- Surgical asepsis (sterile technique) eliminates all microorganisms and their spores. It is required for invasive procedures such as inserting a urinary catheter or handling a surgical wound.
Hand Hygiene: The 5 Moments
Hand hygiene is the single most effective infection-prevention measure. It uses alcohol-based hand rub (preferred when hands are not visibly soiled) or soap and water. The World Health Organization defines “My 5 Moments for Hand Hygiene”:
- Before touching a patient
- Before a clean or aseptic procedure
- After body-fluid exposure risk
- After touching a patient
- After touching the patient’s surroundings
Wash with soap and water when hands are visibly dirty or after caring for patients with spore-forming organisms such as C. difficile.
Standard and Transmission-Based Precautions
Standard precautions apply to every patient, every time. They treat all blood, body fluids, secretions, non-intact skin, and mucous membranes as potentially infectious, and include hand hygiene, appropriate PPE, safe injection practices, and respiratory etiquette.
Transmission-based precautions add protection when a specific route is known or suspected:
| Type | Spread by | Key protection |
|---|---|---|
| Contact | Touch (e.g., MRSA, C. difficile) | Gown and gloves |
| Droplet | Large respiratory droplets (e.g., influenza) | Surgical mask within ~6 feet |
| Airborne | Tiny airborne particles (e.g., tuberculosis, measles) | N95 respirator; negative-pressure room |
Personal Protective Equipment (PPE)
The order of putting on and removing PPE matters because doffing is when contamination is most likely.
- Donning (putting on): gown → mask or respirator → goggles/face shield → gloves.
- Doffing (taking off): gloves → goggles/face shield → gown → mask/respirator, performing hand hygiene during and after.
Gloves come off first because they are the most contaminated; the mask comes off last because the room air may still hold the hazard.
Maintaining a Sterile Field
For surgical asepsis, a sterile field is created and guarded. Core rules: keep sterile items in view and above waist/table level; treat the outer 1-inch border as non-sterile; never reach over or turn your back on the field; and consider any field wet by an unsterile liquid to be contaminated. Only sterile items touch sterile items.
Asepsis in Everyday Tasks
Most patient contact uses medical asepsis: clean hands, clean gloves, and clean equipment for tasks such as bathing, feeding, and taking vital signs. Surgical asepsis is reserved for procedures that break the body’s natural barriers or enter sterile spaces — inserting a urinary catheter, changing certain wound dressings, or drawing up an injection. Knowing which level a task demands prevents both under-protection (an infection risk) and needless waste of sterile supplies. When in doubt, a nurse follows facility policy and treats the more invasive interpretation as the safer choice.
Clinical Relevance
These practices are woven into daily care. A nurse performs hand hygiene dozens of times per shift, selects gloves or a gown based on the task, and dons a respirator before entering an airborne-precaution room. Understanding the chain of infection lets caregivers reason about why each step matters rather than memorizing rules. That reasoning is what makes precautions reliable under pressure — during a busy admission, an emergency, or a fast-moving outbreak — and it protects vulnerable patients, coworkers, and the nurse’s own family at home.