Why is hand washing necessary before performing any work in a hospital?

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E6 Nursing Vital Signs p. 37-39
E6 Nursing Fundamentals Potter Perry 12e Part 2 p. 234-236
E6 Parks TextBook of Preventive & Social Medicine part 1 — Subpart C (pp 404-604 of 604) p. 26-28
Practise the full UP CHO - 2018
Attempt every question from this paper in a timed mock, then review the full solution for each one.