Preventing and Controlling the Transmission of Infectious Agents
The hierarchy of precautions
Standard precautions apply to every patient: hand hygiene, gloves for contact with blood or body fluids, gown and eye protection when splash is likely, safe sharps handling, and respiratory hygiene/cough etiquette. Transmission-based precautions are added on top. Contact: MRSA, VRE, CRE, C. difficile, norovirus, RSV, scabies, uncontained wound drainage - gown and gloves, private room or cohorting. Droplet: influenza, pertussis, meningococcal disease, mumps, rubella, diphtheria - surgical mask; the door may stay open. Airborne: pulmonary or laryngeal TB, measles, varicella, disseminated zoster - N95 or PAPR inside a negative-pressure AIIR with at least 12 air changes per hour and the door closed; susceptible staff should not enter.
Hand hygiene
Know the WHO Five Moments and the exceptions: soap and water, not alcohol, for C. difficile and norovirus because alcohol does not reliably kill spores and non-enveloped viruses; soap and water whenever hands are visibly soiled. Gloves never replace hand hygiene.
Practical details
Don PPE before entry and remove before exit; perform a user seal check every time an N95 is donned. Duration matters: measles and varicella precautions continue for the full incubation window after exposure, and immunocompromised hosts shed longer.
Traps
The most common errors are assigning the wrong category (treating meningococcus as airborne) and forgetting that a surgical mask suffices for droplet but not airborne pathogens. Cohort only patients with the same organism.
Rule of thumb: Ask two questions - how does it travel, and how long does it stay infectious? Those two answers set both the precaution type and the discontinuation date.