The Ethics of Infection – NYTimes.com.

“PRIMUM NON NOCERE” or “First, do no harm” is supposed to be the guiding principle of health care workers. And within civil societies, at least, not harming others is considered every person’s moral, ethical and even legal responsibility.

The heated debate over whether it’s responsible for health care workers who treated Ebola patients to go grocery shopping or bowling or get on a cruise ship before the end of the disease’s 21-day incubation period raises a larger question: What is everyone’s duty to prevent transmission of infectious diseases?

Is it ethical to go to the gym when you have a cold, visit a nail salon when you have a foot fungus or board an airplane with a stomach bug? What about the morality of sending your kids to school when they have, say, a green runny nose or were not vaccinated? Are you a bad person if you don’t get a flu shot?

When it comes to “do no harm,” the problem is defining harm and the risk of inflicting it, as well as what constitutes reasonable measures to impose on someone to minimize that risk.

“Risk is a function of two things — probability that harm will occur and severity of that harm, should it transpire,” said Lawrence O. Gostin, a professor of law at Georgetown University who specializes in public health law and human rights.

And those two factors, he said, have a rough inverse relationship. That is, the more severe the potential harm, the less probability, or risk, we are willing to assume — much less allow someone else to assume on our behalf…