I don't understand

I work in a hospital. Every year I have to have a TB skin test, even though I am not directly involved in patient care. Everyone at our hospital has to take this test--even volunteers and students. We also have an employee health/infection control nurse to deal with this sort of situation. I thought all this was required by law. Maybe the laws are different in Virginia. But I'd like to know how a Virginia nurse died of tuberculosis after exhibiting symptoms of active TB in a health care setting for months. This really seems to have been preventable, and somewhere the system broke down and this individual--and possibly many more--suffer because of it.