Preventing/Controlling the Transmission of Infectious Agents
Domain 3 - Preventing/Controlling the Transmission of Infectious Agents
This domain tests whether you can select the right precaution tier for a given organism, apply it for the right duration, and get the practical details - PPE, hand hygiene, room assignment - right.
Core rules
- Standard precautions apply to every patient: hand hygiene, gloves for contact with blood/body fluids, gown and eye protection when splash is likely, safe injection practices, respiratory hygiene/cough etiquette.
- Contact - MRSA, VRE, C. difficile, CRE, scabies, RSV, norovirus: gown and gloves at the door, dedicated equipment.
- Droplet - influenza, pertussis, mumps, rubella, meningococcal disease, diphtheria: surgical mask within about 1.8 m (6 ft); door may remain open.
- Airborne - pulmonary/laryngeal TB, measles, varicella, disseminated zoster: AIIR with ≥12 air changes per hour, fit-tested N95 or higher, door closed.
- Hand hygiene: alcohol-based rub for most situations; soap and water when hands are visibly soiled and for C. difficile/norovirus, because alcohol does not reliably kill spores.
- Duration: until symptoms resolve or per organism-specific criteria (TB until three negative AFB smears on effective therapy; varicella until lesions crust; influenza 7 days from onset or 24 h afebrile).
Worked example
An ED patient with fever, weight loss, and a cavitary infiltrate on chest imaging. Reasoning: suspect pulmonary TB, so place the patient in an AIIR immediately, put a surgical mask on the patient for transport, use an N95 for staff, and order AFB smears and NAAT. Do not wait for results to start airborne precautions.
Traps
Using alcohol rub for C. difficile; applying droplet instead of airborne precautions for measles or varicella; leaving visitors and transport staff out of PPE requirements; discontinuing precautions after a set number of days rather than on clinical or microbiologic criteria.