The chain of infection, standard and transmission-based precautions, the order for putting on and removing PPE, hand hygiene, sterile technique and HAIs.
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Must-know for the exam
✓Hand hygiene is the single most effective way to prevent healthcare-associated infection — follow the WHO 5 moments.
✓Standard precautions apply to every patient regardless of diagnosis, treating all blood and body fluids as potentially infectious.
✓Transmission-based precautions: Contact (for example MRSA, C. difficile), Droplet (for example influenza, meningococcus), Airborne (TB, measles, varicella).
✓Airborne precautions need a negative-pressure room and a fit-tested N95 respirator; droplet precautions need a surgical mask within about 1-2 metres.
✓Use alcohol hand rub for most situations, but wash with soap and water for C. difficile and other spores, which alcohol does not kill.
✓Don PPE in order (gown, mask, eye protection, gloves) and remove it gloves-first with hand hygiene after — the sequence protects you.
How the exam frames infection-control questions
Infection prevention and control is high-yield and unusually predictable on this exam: the examiner is nearly always testing whether you can identify the correct PRECAUTION for a given organism, choose the right PPE and patient placement, break the CHAIN OF INFECTION at the right link, or protect a patient or yourself from cross-transmission. Because the rules are standardised, the questions reward memorised categories more than reasoning — but you must apply them to a scenario.
A dependable frame for any infection-control stem:
•Identify the ORGANISM and its main route of spread. The disease named in the stem tells you the precaution: contact, droplet or airborne (on top of standard precautions, which always apply).
•Match the PPE and the ROOM to that route. Airborne needs an N95/respirator and a negative-pressure room; droplet needs a surgical mask and a private room (or spatial separation); contact needs gown and gloves.
•Break the CHAIN. When asked what most reduces transmission, the answer is usually the measure that breaks a link — most often HAND HYGIENE, but also isolating a source, or protecting a susceptible host.
•Protect the vulnerable. For an immunocompromised (neutropenic) patient the question flips to PROTECTIVE measures that keep organisms AWAY from the patient.
Reference figures quoted here are widely used values (for example, an airborne isolation room provides negative pressure with roughly 6–12 air changes per hour). Facilities and guidelines differ, so read every number against your own local DHA-aligned policy before acting.
The chain of infection — the framework behind every intervention
Every infection-control measure exists to BREAK a link in the chain of infection. Knowing the six links lets you answer 'what is the best way to prevent transmission?' by naming the link being broken:
•INFECTIOUS AGENT — the pathogen (bacteria, virus, fungus, parasite). Broken by treatment, disinfection and sterilisation.
→Using alcohol hand rub for C. difficile instead of soap-and-water handwashing, which is needed to remove spores.
→Placing a droplet-precaution patient in a negative-pressure airborne room, or an airborne patient in a normal room — match the room to the transmission route.
→Removing PPE in the wrong order or touching the face; gloves come off first, mask last, with hand hygiene throughout.
→Reusing or wearing the same gloves between patients or tasks instead of changing them and performing hand hygiene each time.
→Treating standard precautions as optional for a clean-looking patient — they apply to everyone, every time.
•RESERVOIR — where the organism lives and multiplies (people, equipment, water, surfaces). Broken by cleaning, disinfection, and managing the source.
•PORTAL OF EXIT — how it leaves the reservoir (respiratory secretions, blood, faeces, wound drainage). Broken by covering coughs, containing secretions and safe waste handling.
•MODE OF TRANSMISSION — how it travels (contact — direct or indirect; droplet; airborne; also vehicle and vector). This is the link precautions and PPE target most directly, and HAND HYGIENE breaks the commonest route (indirect contact via hands).
•PORTAL OF ENTRY — how it gets into a new host (broken skin, mucous membranes, invasive devices, the respiratory or GI tract). Broken by aseptic technique, wound care and device care.
•SUSCEPTIBLE HOST — the next person at risk (the very young, older adults, the immunocompromised, those with chronic disease or invasive lines). Broken by immunisation, nutrition, treating underlying disease and protecting the vulnerable.
The single most important exam takeaway: HAND HYGIENE breaks the mode-of-transmission link and is the most effective single action to prevent healthcare-associated infection. When a question asks for the BEST way to reduce spread and hand hygiene is an option, it is almost always correct.
