[NYTimes] “Wash your hands when you shake hands; cover your mouth when you cough,” President Obama urged us at last Wednesday’s news conference when discussing the swine flu. “I know it sounds trivial, but it makes a huge difference. If you are sick, stay home. If your child is sick, keep them out of school. If you are feeling certain flu symptoms, don’t get on an airplane, don’t get on a — any system of public transportation where you’re confined and you could potentially spread the virus.” Is such modest, homespun advice merely good manners, or is it a moral injunction?

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This guidance rises to the level of ethics because it concerns the effect of our actions on other people. Etiquette codifies behavior that is merely a matter of form and hence apt to have a trivial impact on others. Whether or not to rob a guy? Ethics. Whether or not to curtsey after robbing a guy? Etiquette. Similarly, the old-school demand that a man on a bus surrender his seat to a woman — any woman, no matter how robust — is etiquette, a social convention (and a sexist one at that). A better approach is for a seated passenger, man or woman, to offer a seat to anyone in need, regardless of gender — a frail older man, a very pregnant woman, a weary Joe Biden (should he muster his courage and return to public transportation). This is ethics (albeit small-scale ethics): an effort to assist those who need it.

And so is Obama’s hand-washing recommendation, echoing the wise counsel that our parents gave us when we were children and that Ignaz Semmelweis gave to medical students in the maternity clinic at the Vienna General Hospital in 1847. It is an ethical imperative, meant to mitigate the harm we might do to others. That hand-washing also diminishes your own chance of becoming ill makes it more desirable, though it does not further elevate the moral status of the act. In ethics, intent counts; the reason why you wash your hands matters. (That’s not to deny, of course, the virtue of sparing the community the costs of your infirmity — medical care, missed work — a rationale sometimes used to justify seatbelt or helmet laws.)

Those presidential dictates, while fundamentally ethical, are not universally applicable. Some employees, particularly low-wage workers, risk losing pay or even getting fired if they stay home from work to avoid infecting their coworkers. If we expect individuals to act ethically, we have a societal obligation to protect them when they do — for instance, by guaranteeing paid sick days to all.

Another argument for a community response, for the practice of civic virtue: even if someone displays impressive individual rectitude, he may still unknowingly infect other people with swine flu (or, if you prefer a more pork-chop-friendly designation, the H1N1 virus). Dr. Michele Barry, the dean of Global Health at Stanford University, says, “You may not be aware you are transmitting it early on.” People can be contagious for as long as six days before displaying any symptoms — and, she adds, “longer in kids and immuno-compromised folks.”

Some healthy people have taken aggressively individualistic action, asking a friend or relative who is a doctor for prescriptions for Tamiflu, an antiviral medication, to keep around the house just in case. To make such a request is unwise, to honor it unethical. In most cases, doctors “should certainly not be in the business of writing prescriptions for those they have neither examined nor taken a medical history” from, says Dr. Tia Powell, who is the director of the Montefiore-Einstein Center for Bioethics. And while it can be awkward for a doctor to turn down the aunt who will host the family’s next Thanksgiving dinner, that is what medical ethics requires (as I discussed in “The Ethicist” in 2005, responding to a query about avian flu).

A healthy person should not ask such a thing even of his or her own physician. To hoard antiviral medications can make them unavailable to those in immediate need. Temporary local shortages have been reported from New York to Honolulu. Even if there were unlimited supplies of antiviral agents, Barry would caution against their prophylactic use, except by people traveling to the center of the epidemic, because using such medications improperly can breed Tamiflu-resistant strains of the virus.

Thus some individual actions, like the presidentially endorsed washing of hands, are genuinely ethical, while others, like stocking up on antiviral medications, are not. Each must be judged on its merits. What’s more, universally esteemed acts do not obviate the need for community actions. And even those we deem outside the realm of ethics, that we consider to be matters of etiquette, can still be valuable social lubricants. Samuel Johnson was a great defender of politeness, calling it “fictitious benevolence” and asserting that “the want of it never fails to produce something disagreeable.”