To fight the spread of germs, doctors should ditch the handshake and greet their patients with a fist bump instead, a new study says.
Through a series of tests, researchers at the Institute of Biological, Environmental and Rural Sciences at Aberystwyth University in Wales documented that fist bumps are 20 times more hygienic than handshakes. They are also 10 times cleaner than high-fives, according to results published online Monday in the American Journal of Infection Control.
Volunteers donned sterile gloves and dunked their hands into a soup of de-fanged Escherichia coli bacteria. Then they shook hands, high-fived or fist-bumped with one another.
The handshakes transferred an average of 124 million colony-forming units of E. coli. That was almost twice as high as for high-fives and about 20 times more than with fist bumps, Sara Mela and David Whitworth discovered.
In part, this was due to the large contact area of handshakes (24.4 square inches, on average). The greater the contact area, the more bacteria moved from hand to hand, but that wasn’t the whole story.
For instance, the duration of the greeting matters. Handshakes last longer – 3 seconds – than high-fives or fist bumps. When fist bumps were prolonged to 3 seconds, more E. coli spread from hand to hand. (However, lengthening a high-five didn’t make it any germier.)
The researchers didn’t conduct their tests with any pathogens that were actually dangerous, but they wrote that they would probably get similar results if they had tested flu virus particles or “other pathogenic microorganisms.”
Indeed, there is some evidence that fist bumps spread fewer germs than handshakes under actual hospital conditions.
In a pilot study, researchers from West Virginia University asked two health care workers to make their way from a hospital lobby to a surgical ward on the fifth floor. Along the way, the volunteers pushed elevator buttons, used door handles and touched other potentially germy surfaces.
Once they got to the surgical floor, they each shook hands with 20 other health care workers who didn’t know what the researchers were trying to measure. The 20 hand-shakers were asked to wash their hands, then placed their “clean” hands in a microbiological growth medium to see how many germs survived.
Then the whole experiment was repeated, this time with the two health care workers greeting their colleagues with fist bumps instead of handshakes. (They followed the exact same route from the hospital lobby to the surgical ward.) The 20 fist bump recipients then washed their hands and placed their fists in the growth medium.
The West Virginia researchers found that the people who shook hands had four times as many pathogens on their hands as the people who fist-bumped, according to results published last year in the Journal of Hospital Infection.
But getting doctors to switch from handshakes to fist bumps won’t be easy. Studies have shown that patients feel more calm after shaking hands with their doctor, and some hospitals encourage physicians to greet patients this way to promote a sense of empathy.