Pressing the flesh

 From The Economist

Changing greetings could slow Covid's spread. But handwashing is essential.

In 1439 King Henry VI of England banned kissing as a greeting to stop the spread of the Black Plague. Today, as covid-19 spreads around the world, authorities are encouraging similar measures to fight infection. In China, to avoid hand-shaking, people are being told to greet one another with a gong shou gesture, where a palm is folded over the opposite fist. In the Gulf, citizens are saying hello with a wave rather than the traditional “nose to nose” greeting. And in Italy and France, friends and acquaintances are eschewing the customary peck on both cheeks.

Such efforts are more effective than they might seem. A paper published in 2014 explored how greeting rituals spread infectious diseases. David Whitworth and Sara Mela, two biologists at Aberystwyth University in Wales, dipped a glove in bacteria, before using it to greet another person wearing a sterile glove. Bacteria can be transmitted in a similar way to the new coronavirus. They found that a handshake transfers almost twice as much bacteria as a high five, which in turn transmits twice that of a fist bump. The duration of greetings matters, too. Stronger and longer handshakes transfer more bacteria than weaker, shorter ones. The same goes for high fives.