It's illegal to work around food when showing symptoms of contagious diseases. Why not the same for everyone else? Each person who gets a cold infects one other person on average. We could probably cut infection rates and the frequency of colds in half if sick people didn't come in to work.
And if we want better biosecurity, why not also require people to be able to reschedule flights if a doctor certifies they have a contagious disease?
Due to the 'externalities', the case seems very compelling.
Moving my commentary to a separate comment, so as to disambiguate votes on my commentary and the original argument.