3.3 Transmission-Based Precautions & Facility Isolation
Key Takeaways
- Transmission-Based Precautions (Contact, Droplet, Airborne) are implemented empirically based on clinical syndromes prior to laboratory confirmation and are always used in conjunction with Standard Precautions.
- Contact Precautions require a single-patient room (or cohorting), gown and gloves upon room entry, dedicated non-critical medical equipment, and special disinfectant selection for pathogens like MRSA, VRE, C. difficile, CRE, and scabies.
- Droplet Precautions mandate a single room, spatial separation of >3 to 6 feet, and wearing a surgical mask upon entry for infections transmitted by large respiratory droplets, such as influenza, Bordetella pertussis, and Neisseria meningitidis.
- Airborne Precautions require placement in an Airborne Infection Isolation Room (AIIR) featuring negative air pressure (>=2.5 Pa), >=12 air changes per hour (ACH) for new construction, direct exterior exhaust, closed room doors, and fit-tested N95 respirators or PAPRs for personnel caring for patients with TB, measles, varicella, or disseminated zoster.
- Protective Environment (PE) rooms utilize positive air pressure, HEPA filtration (99.97% efficient at 0.3 µm), and >=12 ACH to protect severely immunocompromised patients (such as allogeneic hematopoietic stem cell transplant recipients) from environmental fungal spores (Aspergillus).
3.3 Transmission-Based Precautions & Facility Isolation
When Standard Precautions alone are insufficient to prevent the transmission of highly contagious or epidemiologically significant pathogens, healthcare facilities implement Transmission-Based Precautions. Transmission-Based Precautions are categorized into three primary categories based on pathogen transmission routes: Contact Precautions, Droplet Precautions, and Airborne Precautions.
A critical mandate in infection prevention is that Transmission-Based Precautions must be applied empirically at the first presentation of clinical symptoms suggestive of an infectious disease (e.g., acute diarrhea, generalized rash, meningeal signs, or unexplained pulmonary infiltrates), rather than waiting for confirmatory microbiological laboratory results.
1. Contact Precautions
Designed to prevent transmission of infectious agents spread by direct or indirect contact with the patient or the patient's environment.
Clinical Indications
- Multidrug-resistant organisms (MDROs): MRSA, Vancomycin-resistant Enterococcus (VRE), Carbapenem-resistant Enterobacterales (CRE), Candida auris.
- Enteric pathogens: Clostridioides difficile, Norovirus, Rotavirus, Escherichia coli O157:H7.
- Skin/ectoparasitic infestations: Scabies, Impetigo, Lice, Uncontained major abscesses or pressure ulcers.
- Viral infections: Respiratory Syncytial Virus (RSV) in infants/children, Cutaneous Herpes simplex.
Requirements
- Patient Placement: Single-patient room preferred. When single rooms are unavailable, cohort patients infected with the same pathogen (provided they are not co-infected with another MDRO).
- PPE: Don gown and gloves prior to entering the patient room. Doff PPE and perform hand hygiene prior to exiting.
- Patient Equipment: Dedicate non-critical patient care equipment (blood pressure cuffs, stethoscopes, thermometers) to the single patient. If shared equipment is unavoidable, clean and disinfect thoroughly with an EPA-registered disinfectant before use on another patient.
- Environmental Decontamination: Ensure daily cleaning of high-touch surfaces. For C. difficile and Norovirus, use an EPA-registered sporicidal disinfectant (e.g., sodium hypochlorite/bleach).
2. Droplet Precautions
Designed to prevent transmission of pathogens spread through close respiratory or mucous membrane contact with large respiratory droplets (>5–10 µm).
Clinical Indications
- Bacterial infections: Neisseria meningitidis (meningococcal meningitis/septicemia), Bordetella pertussis (whooping cough), Haemophilus influenzae type b, Mycoplasma pneumoniae, Group A Streptococcus pharyngitis/pneumonia in infants.
- Viral infections: Influenza virus, Mumps, Rubella, Parvovirus B19, Adenovirus.
Requirements
- Patient Placement: Single-patient room preferred. Spatial separation of at least 3 to 6 feet between infected patient and other patients if cohorting is necessary.
- PPE: Don a surgical mask (isolation mask) upon entry into the patient room. Eye protection (goggles or face shield) should be added if splashes/sprays are anticipated.
- Room Ventilation: Special air handling and negative pressure are not required; room door may remain open.
- Patient Transport: Limit transport outside the room to medically necessary purposes. Apply a surgical mask to the patient during transport.
3. Airborne Precautions
Designed to prevent transmission of infectious agents that remain infectious over time and distance when suspended in the air via tiny droplet nuclei (<5 µm).
Clinical Indications
- Mycobacterium tuberculosis (pulmonary or laryngeal TB).
- Measles (Rubeola) virus.
- Varicella-zoster virus (Chickenpox / primary varicella).
- Disseminated Herpes zoster or localized zoster in immunocompromised hosts.
- Emerging pathogens: Severe Acute Respiratory Syndrome (SARS-CoV), MERS-CoV, Smallpox.
Requirements & Engineering Controls
- Airborne Infection Isolation Room (AIIR):
- Negative Pressure: Maintained relative to surrounding hallways (minimum negative pressure differential of -2.5 Pascals or -0.01 inches of water gauge).
- Air Change Rate: Minimum of 12 Air Changes per Hour (ACH) for new construction/renovation (minimum 6 ACH for older existing facilities).
- Exhaust: Direct exhaust of air to the exterior of the building away from air intakes, or recirculation through high-efficiency particulate air (HEPA) filtration.
- Door Control: Room door must remain strictly closed at all times.
- Monitoring: Continuous visual or electronic pressure monitoring devices (e.g., ball-in-tube indicator or digital manometer).
- Respiratory Protection: Healthcare personnel must wear fit-tested N95 filtering facepiece respirators or Powered Air-Purifying Respirators (PAPRs) prior to room entry.
- Immune Status: Susceptible staff should not enter rooms of patients with varicella or measles if immune staff are available.
4. Protective Environment (PE)
A specialized isolation environment designed to minimize fungal spore exposure for severely immunocompromised patients, specifically allogeneic hematopoietic stem cell transplant (HSCT) recipients.
Engineering Controls for PE Rooms
- Positive Pressure: Maintained relative to adjacent hallways (positive pressure differential >12.5 Pa).
- HEPA Filtration: Central supply air filtered through HEPA filters capable of removing 99.97% of particles down to 0.3 µm in diameter (targeting environmental mold spores like Aspergillus).
- Air Change Rate: Minimum of 12 ACH.
- Well-Sealed Room: Sealed walls, floors, ceilings, and windows to prevent infiltration of ambient air.
- Prohibitions: Plants, dried flowers, and fresh unwashed produce are prohibited due to fungal spore contamination risks.
Summary of Isolation Precautions & Engineering Requirements
| Precaution Type | Primary Target Pathogens | Required PPE | Room Air Pressure | Ventilation / Air Changes |
|---|---|---|---|---|
| Contact | MRSA, VRE, C. difficile, CRE, Scabies | Gown & Gloves upon room entry | Neutral / Standard | Standard building HVAC |
| Droplet | Influenza, N. meningitidis, Pertussis, Mumps | Surgical mask upon room entry | Neutral / Standard | Standard building HVAC |
| Airborne | TB, Measles, Varicella, Disseminated Zoster | Fit-tested N95 respirator or PAPR | Negative relative to hallway (>=2.5 Pa) | >=12 ACH (new); Direct exhaust or HEPA |
| Protective Environment | Allogeneic HSCT patients (prevention of Aspergillus) | Standard (Mask if staff ill) | Positive relative to hallway (>12.5 Pa) | >=12 ACH with HEPA filtration (99.97% at 0.3 µm) |
Which set of engineering controls is strictly required for an Airborne Infection Isolation Room (AIIR) housing a patient with active pulmonary tuberculosis?
A patient is admitted with fever, nuchal rigidity, and petechial rash. The physician suspects Neisseria meningitidis meningitis. Which transmission-based isolation precaution must be empirically initiated immediately?
Which room specification is unique to a Protective Environment (PE) designed for an allogeneic hematopoietic stem cell transplant (HSCT) recipient?
When caring for a patient under Contact Precautions for Vancomycin-resistant Enterococcus (VRE), what is the requirement regarding non-critical medical equipment such as blood pressure cuffs?