When it comes to avoiding the transmission of swine flu—without awkwardness or rudeness—perhaps the Samoans are best prepared.

“;In Samoa, people do not touch when they greet each other,”; the linguistic anthropologist Dr. Alessandro Duranti says.

There is, of course, a catch: “;When people whom they respect highly come into a house, they sit down across from you, and there is an elaborate ceremonial greeting: mentioning each person's titles and social connections, one at a time, usually for an extended period.”;

For those outside Samoa, the era of swine flu poses the thorny challenge of how to express cordiality, friendship, even love—while staying, as the authorities recommend, at least three to five feet away from anyone who coughs, sneezes or might otherwise show signs of infection with the H1N1 virus.

As the world braces for a second wave of the swine flu that broke out in the spring and resulted in the deaths of more than 2,100 people worldwide, the disease is altering long-established patterns of everyday greeting. Handshakes have been cut short, kisses aborted. Warm embraces have been supplanted by curt pats on the back.

The school district in Glen Cove, N.Y., is discouraging students from exchanging high-fives. In Spain, the health minister has urged citizens to forgo the customary peck on both cheeks. Officials from Lebanon to Kuwait have called for Muslims celebrating Ramadan not to hug excessively.

New York City—where Mayor Michael R. Bloomberg this week announced a series of steps to prepare for a resurgence of the virus—has no formal stance on touching.

“;Kids touch each other, and that's the real world,”; the mayor said on Tuesday, when asked about the matter. “;And I'm not so sure you want a kid that doesn't want to high-five or hug or something. But I won't get involved in that. I think the practical aspect is that kids, whether on the playground or in school, tend to get close to each other, and hopefully parents have taught them that when they cough, cover their mouth, or when they sneeze, cover their nose.”;

The problem, doctors say, is when you shake someone else's hand after that sneeze or that cough, thereby transmitting the virus.

“;The danger isn't that it's on your hands,”; said Dr. Philip L. Graham III, a pediatric epidemiologist at New York-Presbyterian Hospital. “;The danger is that all of us, many hundreds of times a day, rub our hands over our faces. People touch their faces a lot more than they think.”;

When someone with the flu sneezes or coughs without covering the face, the virus is sprayed out in tiny airborne droplets that travel three to five feet before hitting the ground. So a face-to-face conversation could result in infection. (The virus can survive on, say, a phone headset or a computer keyboard for hours, and up to a day or so.)

If touching can't be avoided, a fist-bump is probably safer than a handshake, which in turn is better than a hug or—at worst—a kiss. “;The closer your mucus membranes come to the other person's mucus membranes, the risk is going to increase,”; Graham said.

He added: “;You can't walk away from a sick kid who wants to hug you. You hold your breath and cringe.”;

Kenneth Bromberg, chairman of pediatrics and director of the Vaccine Research Center at the Brooklyn Hospital Center, put it this way: “;The danger is exchanged secretions. The closer you get to the site of the flu, the higher the risk.”;

He added, “;It's OK to go around shaking hands, but before and after, you want to wash your hands.”;

Some cultures have greeting rituals that may make them better prepared to deal with swine flu. Dr. Arthur Kleinman, a medical anthropologist at Harvard who studied the SARS outbreak in China and Hong Kong in 2002 and 2003, noted that some people stopped touching doorknobs or pushing elevator buttons without gloves, and that taxicabs refused to pick up not only those who were sick, but also doctors and nurses.

But the Chinese do not tend to hug much, and to avoid infection, many Chinese could resort to a classical greeting that conveys respect and esteem: palm and fingers of one hand wrapped around the fist of the other, both hands shaking up and down. A gesture of welcome in Arab culture, Kleinman noted, is an upward movement of the hand, touching one's own chest or face.

Even so, Kleinman said, “;Globalization has made the handshake very, very widespread.”;

So much so, said Duranti, the anthropologist who has studied Samoa, that refusing an extended hand can be a grave social violation.

“;You can start out not wanting to shake hands or hug, but if the other person leans over, it becomes more and more difficult to decline,”; said Duranti, who is dean of social sciences at the University of California, Los Angeles. “;You are violating a social expectation in a way that is pretty dramatic.”;

The person declining the handshake can be forthright. “;You are actually doing them a favor: 'I'm not going to shake your hand, hug you, or kiss you because I have a cold.' I've seen that happen,”; Duranti said. “;That presupposes that both parties believe in the theory of germs.”;

Duranti said one of his colleagues, a sociologist, declined to shake his hand last spring at the height of the swine flu anxiety. “;He said, 'No, we don't do that anymore,' and he did some kind of very formal, awkward pat on the back,”;' Duranti recalled. “;He did it with a half-smile to mediate the rejection of my hand going out. But it was a little ridiculous.”;

In an episode of “;Late Show With David Letterman”; broadcast on Monday, the comedian and actor Howie Mandel said he now offers a fist-bump in lieu of a handshake. But instead of responding in kind, Mandel said, some people have grabbed his fist and shaken it. “;It's awkward, because then I have to say, 'Let go,' “; he told Letterman. “;That or just, 'Release me.' “;

The elbow nudge might be a better option.

“;When my hands have been full, I've greeted people elbow to elbow,”; said Philip M. Tierno Jr., director of clinical microbiology and immunology at the New York University Langone Medical Center and author of “;The Secret Life of Germs”; (Atria, 2001).

He added: “;Saluting is good. Bowing is perfectly acceptable. So too, I think, is just saying hi.”;