In their experiments, the scientists found that clasping hands transferred 10 times more germs from one person to the other than what is known as a fist bump. They suggest the more casual exchange might suffice as a cultural substitute for the firm gripping of hands.
The findings are published in the August issue of the American Journal of Infection Control.
"Adoption of the fist bump as a greeting could substantially reduce the transmission of infectious diseases between individuals," corresponding author David Whitworth, a researcher with the Institute of Biological, Environmental, and Rural Sciences at Aberystwyth University in the United Kingdom, said in a journal news release.
"It is unlikely that a no-contact greeting could supplant the handshake," Whitworth acknowledged. "However, for the sake of improving public health we encourage further adoption of the fist bump as a simple, free and more hygienic alternative to the handshake."
One expert in the United States agreed.
"From a medical and social viewpoint, fist bumping is the way to go in exchanging social pleasantries while decreasing the transmission of bacteria and viruses everything from common colds to MRSA can be transmitted by handshakes," said Dr. Sampson Davis, an emergency room physician at The Meadowlands Hospital Medical Center in Secaucus, N.J.
"We touch door knobs and hand rails multiple times throughout the day," he said. "We sneeze and cough into our hands and then we shake hands which serves as a transport of transmission of these germs. The fist bump is a quick interaction and decreases germ transmission."
However, another expert was not convinced by the new findings.
"Hand-to-hand contact is a known way of spreading germs," said Dr. Len Horovitz, a pulmonary specialist at Lenox Hill Hospital in New York City. "The issue is that unwashed hands carry germs, and the recipient touches their face and introduces germs into the body. Hand bumping may not be better insurance against spreading infection," he added.
To test what type of greeting might spread the most germs from one hand to another, one researcher would dip a gloved hand into a container brimming with a fairly harmless strain of E. coli bacteria. That researcher would then shake, fist bump or high-five the gloved, but clean, hand of another researcher. The glove that had been germ-free to start with was then tested for levels of E. coli bacteria.
The handshake turned out to be the dirtiest exchange of all, spreading twice as many germs as a high-five and 10 times as many germs as a fist bump, the investigators found.
Using paint in a second round of tests, the researchers found that more of each person's hand touched the other person's hand in a handshake, and that they tended to last longer. They theorized that those two facts might explain why handshakes are the least sanitary exchange.
This latest finding broadens the recent call from the Journal of the American Medical Association to ban handshakes in hospitals, according to the news release.
Health care providers can spread harmful germs to patients through hand contact, and lead to health care-associated infections, which are one of the leading causes of preventable harm and death in the United States, the news release said.
One in 25 hospitalized patients develops such an infection, and 75,000 patients with these infections die during their hospitalization each year, according to estimates from the U.S. Centers for Disease Control and Prevention.
Visit the U.S. Centers for Disease Control and Prevention for more on hand hygiene.