Getting this right protects patients from healthcare-acquired infections (which cause approximately 4 million events per year in the EU alone), protects healthcare workers from occupational infection, and prevents the amplification and spread of antibiotic-resistant organisms throughout healthcare facilities. Getting it wrong in either direction causes harm: insufficient precautions allow transmission, while excessive precautions create barriers to care and consume resources disproportionately.
This page covers the full hierarchy of infection control precautions from standard to transmission-based, the specific requirements at each level, the organisms that require each type, the WHO 5 Moments of Hand Hygiene, personal protective equipment selection, and the specific infection control requirements for the most important healthcare-associated pathogens.
Standard Precautions: The Baseline for Every Patient
Standard precautions apply to every patient, every time, regardless of their diagnosis or known infection status. They are based on the principle that any blood, body fluid, non-intact skin, or mucous membrane may carry transmissible pathogens, known or unknown. Standard precautions do not identify "infectious" patients as a distinct category: they define a level of protection that is always applied.
Standard precautions include: hand hygiene (the single most effective infection control measure), gloves for any contact with blood, body fluids, mucous membranes, or non-intact skin, gown when clothing contamination is expected, eye/face protection when splashes of blood or body fluids are possible, safe sharps handling (no recapping, direct to sharps bin), respiratory hygiene and cough etiquette, safe disposal of clinical waste, and decontamination of patient care equipment between patients.
The rationale for universal application is the proven inadequacy of identifying "infectious" patients before care: many patients are infectious without known diagnosis, many patients are colonised with transmissible organisms asymptomatically, and laboratory results are not available at the point of initial care.
The WHO 5 Moments of Hand Hygiene
The WHO 5 Moments of Hand Hygiene framework, developed as part of the WHO's Clean Care is Safer Care programme, defines the specific moments during patient care when hand hygiene is required:
Moment 1: Before touching the patient. Before any contact with the patient or their immediate surroundings.
Moment 2: Before a clean/aseptic procedure. Before performing any aseptic task such as inserting a catheter, placing a central line, or preparing an injection.
Moment 3: After body fluid exposure risk. After contact with blood, body fluids, mucous membranes, wound dressings, or any potentially infectious material. This moment may occur even without glove use if non-intact skin was involved.
Moment 4: After touching the patient. After any physical contact with the patient or their immediate surroundings.
Moment 5: After touching patient surroundings. After contact with any object or furniture in the patient's immediate environment, even if the patient was not touched directly.
Alcohol hand rub (AHR) is the preferred hand hygiene agent for most moments: it is more rapidly effective, less damaging to skin with repeated use, and more accessible at the point of care (provided at each bed space). Soap and water is required after contact with Clostridioides difficile or norovirus, because these organisms are not reliably inactivated by alcohol.
Transmission-Based Precautions: Contact, Droplet, Airborne
When an organism's transmission route requires precautions beyond standard, transmission-based precautions are added. There are three types, which can be combined when an organism has multiple transmission routes.
Contact precautions are required for organisms that transmit by direct physical contact with the patient or indirect contact with contaminated surfaces and equipment. Contact precautions: gloves and gown on entry to the room, single room (or cohort of patients with the same organism), dedicated patient care equipment (or thorough decontamination between patients), enhanced environmental cleaning. Required for: MRSA, VRE, C. difficile, norovirus, scabies, impetigo, ESBL-producing organisms (in some settings), Candida auris.
Droplet precautions are required for organisms that transmit via large respiratory droplets (greater than 5 micrometres diameter) that fall within approximately 1 metre. Single room, surgical mask when within 1 metre of the patient. Required for: Neisseria meningitidis, Haemophilus influenzae, influenza virus, mumps, rubella, Streptococcus pneumoniae, Bordetella pertussis, SARS-CoV-2 (plus enhanced precautions in some guidelines).
Airborne precautions are required for organisms that transmit via small particle aerosols (less than 5 micrometres) that remain airborne and travel further than 1 metre. Single room with negative pressure ventilation (air exhausted outside the building through HEPA filters), fit-tested FFP2 or FFP3 (N95 or above) respirator. Required for: Mycobacterium tuberculosis, measles virus (rubeola), chickenpox (varicella-zoster), disseminated zoster, MERS-CoV, smallpox.
Some procedures generate aerosols from patients with organisms that normally transmit by droplet only. Aerosol-generating procedures (AGPs) including intubation, bronchoscopy, sputum induction, and high-flow nasal oxygen require airborne precautions even for patients with droplet-spread organisms.
Specific Organism-Level Requirements
Clostridioides difficile: contact precautions plus enhanced environmental cleaning with sporicidal agents (sodium hypochlorite at 1,000 to 5,000 ppm, or hydrogen peroxide vapour). Alcohol hand gel does NOT inactivate C. difficile spores: soap and water must be used after C. difficile patient contact. Single room. The patient should remain in single room for the duration of diarrhoea plus 48 hours after diarrhoea resolves (or per local policy).
MRSA: contact precautions. Decolonisation of MRSA-positive patients (nasal mupirocin, chlorhexidine body wash) in high-risk settings (pre-operatively, ICU admission). Healthcare workers colonised with MRSA should be offered treatment. MRSA screening (nasal, groin, perineum, and wound swabs) before elective surgery is standard in the UK for high-risk procedures.
Pulmonary Tuberculosis: airborne precautions. FFP3 (or fit-tested FFP2) respirator for all patient contact. Single negative pressure room. The room should have at minimum 6 to 12 air changes per hour, with air exhausted to the outside. Patient to wear surgical mask when outside their room to reduce droplet/aerosol dispersal.
Norovirus: contact precautions plus soap and water hand hygiene (alcohol not effective). Ward closure when outbreak is suspected (no new admissions to affected ward, no patient transfers until 72 hours after the last case). Specific food handler exclusion policy (food handlers must not work for 48 to 72 hours after last symptoms).
Frequently Asked Questions
What are standard precautions?
Standard precautions are the baseline infection prevention measures applied to all patients regardless of their known infection status. They include hand hygiene, appropriate gloves and gown for contact with blood and body fluids, eye protection for splash risk, safe sharps handling, and safe waste disposal. They are based on the assumption that any patient may carry transmissible pathogens.
What are the WHO 5 Moments of Hand Hygiene?
The 5 Moments are: (1) before touching the patient, (2) before a clean/aseptic procedure, (3) after body fluid exposure risk, (4) after touching the patient, (5) after touching patient surroundings. These moments define exactly when hand hygiene is required during patient care.
Why is soap and water required for C. difficile instead of alcohol gel?
Clostridioides difficile forms spores that are highly resistant to alcohol. Alcohol-based hand rubs do not reliably remove or inactivate C. difficile spores. Soap and water physically removes spores from hands through mechanical action. After any contact with a C. difficile patient or their environment, hand hygiene must be performed with soap and water.
What is an N95 respirator and when is it required?
An N95 respirator (or FFP2/FFP3 in European classification) is a close-fitting particulate respirator that filters at least 95 per cent of airborne particles when fit-tested and worn correctly. It is required for airborne precautions: when caring for patients with tuberculosis, measles, chickenpox, disseminated zoster, or during aerosol-generating procedures on patients with any high-risk respiratory infection.
What organisms require airborne precautions?
Organisms transmitted via small particle airborne aerosols (less than 5 micrometres) that remain infectious at distance: Mycobacterium tuberculosis, measles virus (rubeola), varicella-zoster virus (chickenpox and disseminated zoster), MERS-CoV, and smallpox virus. SARS-CoV-2 requires airborne precautions for AGPs in most guidelines.
What is a negative pressure room?
A negative pressure isolation room maintains a lower air pressure than surrounding corridors. This means air flows into the room through gaps around doors, rather than out. Contaminated air from inside the room cannot escape into the corridor. Exhaust air is HEPA-filtered before release. Negative pressure rooms are used for patients with airborne precaution requirements.
What is decolonisation and when is it used?
Decolonisation reduces or eliminates carriage of a specific organism from body sites. For MRSA, decolonisation includes nasal mupirocin for 5 days (to eliminate nasal carriage) combined with chlorhexidine skin washes. It is used for high-risk patients before major surgery, for ICU patients on admission, and for outbreak control. Decolonisation reduces surgical site infection rates in MRSA-colonised patients undergoing elective procedures.
What is Candida auris and why does it require special precautions?
Candida auris is a multidrug-resistant yeast that emerged globally around 2009. It causes invasive candidiasis in critically ill patients, is frequently resistant to fluconazole and sometimes to multiple antifungal classes, and is remarkable for its persistence in the healthcare environment: it can survive on surfaces for weeks and is not reliably removed by standard cleaning agents. It requires enhanced contact precautions, environmental decontamination with specific disinfectants shown to be effective against C. auris (bleach-based or hydrogen peroxide-based products), and in some settings requires genomic surveillance to track spread.
What is the single most effective infection control measure?
Hand hygiene is the single most important and most evidenced infection control measure. WHO's Clean Care is Safer Care programme estimates that consistently applied hand hygiene at the 5 Moments reduces healthcare-associated infection rates by up to 50 per cent. Despite this, compliance in healthcare settings worldwide averages only 40 to 50 per cent without active programme support.
What is a care bundle?
A care bundle is a set of evidence-based practices that, when implemented together consistently, produce better outcomes than any single practice alone. In infection control, the central line insertion bundle (hand hygiene, maximal sterile barrier precautions, chlorhexidine skin antisepsis, optimal site selection, daily review of line necessity) reduces CLABSI rates by up to 70 per cent. The ventilator bundle reduces ventilator-associated pneumonia similarly.