Transmission
The mechanism by which a pathogen spreads from a reservoir to a susceptible host.
The exam rarely asks you to define transmission; instead it hands you a diagnosis and makes you pick the room, the PPE, and the door. The decisive tell is the organism’s name, not the symptoms — so memorize which bug rides which route. The highest-yield trap is the handful of conditions needing two transmission-based precautions at once: varicella and disseminated zoster are airborne plus contact (localized zoster in an immunocompetent patient is standard precautions only). For SARS-CoV-2, current CDC healthcare guidance calls for an N95, gown, gloves, and eye protection — escalating to an AIIR for aerosol-generating procedures (older banks still label COVID-19 simply “droplet plus contact”). Choosing one precaution when two are required is the classic miss.
Distinguish transmission (the route, one link in the chain of infection) from the pathogen itself (the agent at the chain’s start) — the exam blurs these. A useful hook: “My Chicken Hez TB” — Measles, Chickenpox (varicella), Herpes zoster, TB are the airborne four (though measles and TB stay airborne-only, no added contact).
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