HIV (Human Immunodeficiency Virus) is a retrovirus that targets CD4+ T-lymphocytes, progressively destroying the immune system. AIDS (Acquired Immunodeficiency Syndrome) is the advanced stage defined by CD4 count <200 cells/μL or an AIDS-defining illness. Transmission routes (ONLY these): - Sexual contact with infected fluid (semen, vaginal secretions) - Blood-to-blood (sharing needles, transfusion with unscreened blood) - Mother-to-child (vertical): during pregnancy, delivery, or breastfeeding NOT transmitted by: casual contact, hugging, sharing dishes, toilet seats, mosquito bites, saliva, tears, or sweat. On the exam, writers often pair stable-sounding options with unstable data—notice the mismatch before you commit. If the stem names a license or role, reread that line; scope errors are classic trap answers even when the clinical topic is familiar. Run a 60-second scan: breathing work and oxygenation, perfusion and end organs, neuro baseline, likely infection sources, and devices that can fail quietly. When two answers feel partly right, pick the one that reduces imminent harm and matches orders for the role you were given. Train yourself to state the primary risk in one short phrase before you read the options...