2.4 Infection Control and the Chain of Infection

Infection Control Is Tested Twice

Infection control sits inside the 35% Basic Nursing Skills domain on the 2024 NNAAP written outline, and it is also a Critical Element on the Credentia skills evaluation. That double weighting is why it deserves its own section: a candidate can lose written points for not knowing which precaution applies and lose an entire skill for a single contamination error. The Maryland Code of Maryland Regulations (COMAR) also requires pre-clinical instruction in infection control before a trainee ever touches a client, so the Board treats it as foundational, not optional.

The core mental model is the chain of infection — six links that an infection must complete to spread. The CNA's job is to break any one link, and hand hygiene is the most powerful break because it interrupts the mode of transmission for most facility infections.

The Six-Link Chain of Infection

Memorize the chain in order, because written items often ask which link a specific action breaks. Washing your hands between residents breaks the mode of transmission; bagging a soiled brief breaks the portal of exit; keeping a wound dressing clean and dry protects the portal of entry.

Standard Precautions Come First, Every Time

Standard Precautions treat the blood and all body fluids (except sweat) of every resident as potentially infectious, no matter the diagnosis. They include hand hygiene, gloves for any contact with body fluids or non-intact skin, gowns and eye protection when splashing is likely, safe handling of linens and waste, respiratory hygiene (cover coughs), and never recapping needles. You apply them to a healthy-looking resident and a sick one alike, because you cannot tell by looking who is colonized with an organism.

Transmission-Based Precautions and PPE Sequencing

When a specific organism is suspected or confirmed, the nurse adds Transmission-Based Precautions on top of Standard Precautions. Knowing which level matches which germ is a recurring written-exam trap, so anchor the examples.

Worked example — the C. difficile trap. A resident on Contact Precautions has C. diff diarrhea. After care you remove gloves and reach for the alcohol-based hand rub. That is wrong: alcohol gel does not kill C. diff spores. The correct action is soap and water with friction, which physically washes spores away. The same rule applies any time your hands are visibly soiled — soap and water, not gel.

Donning and Doffing PPE in Order

Personal protective equipment (PPE) is only protective if applied and removed in the right sequence. Reversing the order spreads contamination to your skin and clothes.

1. Donning (putting on), cleanest to dirtiest workflow: hand hygiene, then gown, then mask or N95 respirator, then goggles or face shield, then gloves last so they cover the gown cuffs.
2. Doffing (taking off), dirtiest first: gloves, then goggles or face shield, then gown, then mask last because the front of the mask is contaminated and you want it off near the door.
3. Finish with hand hygiene immediately after removing the final item.

A memory hook: you build PPE from the body outward (gown first), and you peel it off contaminated-side-in, gloves first. On the Credentia skills lab, if the evaluator must remind you to put gloves on or take them off, that credit is lost — so build glove timing into the flow rather than relying on a prompt.

Linens, Waste, Sharps, and the Isolation Room

Everyday infection control is mostly about clean-to-dirty discipline. Hold soiled linen away from your uniform, roll it inward so the dirty side is contained, and never shake it (shaking aerosolizes microbes). Place contaminated linen in the appropriate bag at the point of use, not in the hallway. Body-fluid waste goes in biohazard (red) bags; routine trash does not. CNAs do not handle sharps disposal beyond keeping the container upright and reporting when it is three-quarters full — they never reach into a sharps container or recap a needle.

In an isolation room, gather supplies before entering so you do not have to leave and re-enter, use dedicated equipment (a blood-pressure cuff that stays in the room), and disinfect any shared device before it leaves. When transporting a resident on precautions, the resident wears the mask, and you notify the receiving area in advance. The safest written-exam answer for any infection question follows the same order: protect with the correct precaution level, use hand hygiene and PPE in sequence, contain contaminated items clean-to-dirty, and report a break in technique to the nurse rather than ignoring it.