We ALL do this in the medical field. Everyone. All the nurses and docs I know stay home if we're puking sick, have a crazy fever, or are otherwise actually incapacitated. Otherwise we down Tylenol and suck it up. Good idea? No. Why do we do it? Lots of reasons. We don't want our colleagues to have to work short or come in extra, we believe our patients just can't stagger along without us, and/or we work for facilities that, like the last one I worked at, FIRE you if you're sick more than three days in 6 months (that's not much if you get a good knockout flu). People in all fields probably do this, but I always thought it was a bad idea to do it in, eg, the ICU (fever around fresh postop patients? not that good...).