Key risk factors for MRSA colonization include a history of hospitalization (RR: 2.2), prior antibiotic use (RR: 1.4), diabetes mellitus (RR: 4.4), HIV with CD4 < 200 cells/μL (RR: 2.8), invasive procedures (RR: 4.8), and being a nurse compared to a physician (RR: 1.8), all with p < 0.05. The gene discussed is CD4; the disease is diabetes mellitus.