Before Joe Biden departed for his trip to the Middle East last week, White House officials said the president would be limiting physical contact, including shaking hands, as part of COVID-19 precautions.
Yet the president seemed to interchange his greetings, fist-bumping some, while shaking hands with others.
It also highlighted that while its potential demise was predicted in the early days of the pandemic, the handshake has proven to be just too resilient to fade away.
"There's the science. I think there's the fact that it's not only an ingrained habit for a lot of people, but there is also no good replacement," said Andrew Molinsky, a professor of organizational behaviour at Brandeis University's International Business School in Boston.
Molinsky said that among the "portfolio of greetings," which includes the fist bump, the elbow, the smile and wave, "the market share has been dominated and still is dominated by the handshake."
Hard habit to break
"The question then would be why? Is it that the other gestures were not as compelling? Is it a habit that's hard to break? Or is there something inherent about [it]?
"I think it's probably all those."
At the onset of the COVID-19 outbreak, with knowledge about the virus and its transmission in its infancy, one area that was of concern for potential spread was through physical touch and the simple gesture of shaking hands.
That gesture has been a sore spot for some infectious disease specialists long before COVID-19. Microorganisms that might cause infections can live on the surface of the hand, especially the palm. When someone shakes hands, those microbes may be transferred from the skin of one person to the skin of the other.
That by itself is usually harmless, but the threat comes when a person who has just received that germ then touches their face and allows those microbes to get into the mouth and nose, or eyes.
And when the COVID-19 virus emerged it was believed it too would pose the same transmission threat.
"There are lots of different viruses, including respiratory viruses, that can spread through handshakes and contact and these kinds of things," said Stephen Kissler, a research fellow in the department of Immunology and Infectious Diseases at the Harvard T.H. Chan School of Public Health.
"We had every reason to believe that SARS-CoV-2 would behave the same way."
A number of articles in 2020 predicted this virus would finally put an end to the germy gesture, including Time magazine's "COVID-19 Killed the Handshake. What Will Replace It?" And The New Yorker's "In Memoriam: The Handshake."
Dr. Anthony Fauci, the leader of the U.S. response to the COVID-19 pandemic, told the Wall Street Journal in an April 2020 podcast that he didn't believe "we should ever shake hands ever again."
Thinking has changed 'dramatically'
But after the initial fears — and more research — "thinking around this has changed dramatically since the start of the pandemic," Kissler said.
"It really seems from all of the vast amounts of data we've collected up until this point, that the vast, vast majority of infections happen through airborne spread," he said.
"I would say that a handshake is a pretty low-risk thing you can do with respect to COVID."
That's not to say that COVID-19 can't be spread through touch. It's just not that easy, said Linsey Marr, a researcher on the airborne transmission of infectious diseases and a professor at Virginia Tech.
"I think the person who's infected would have to have wiped their nose with their hand or spit on it. Kind of have a lot of virus on there and then shake the other person's hand," the civil and environmental engineering professor said.
"And then the other person touches their eyes or [goes] up their nose or in their mouth."
But Marr said that there are "a lot of losses along the way" and that only some fraction of the virus will transfer to their hands.
"It's not like all of it transfers from one person to the other," she said.
While surfaces were thought to be high-risk for transmission, research shows they play a small role and aerosols are more significant. The bigger concern would be the close contact those shaking hands would have with each other, said Abraar Karan, an infectious disease physician and researcher at Stanford University.
"The concern is not quite as much that someone will have it on their hand and they'll get it on to you. The bigger concern is that you essentially are very close up near somebody and they're breathing near you and you get infected that way," Karan said.
He said while it's "theoretically possible" to transmit the virus through hand-to-hand contact, "I don't think it's a huge concern."
Meanwhile, some research indicates that despite the science, the handshake took a few hits during the course of the pandemic.
And it's not clear whether people are willing yet to embrace the gesture as easily as they did pre-pandemic.
Kristin Nelson, an assistant professor in the department of Epidemiology.at Emory University, co-wrote an article in Science that said some studies of populations in the U.S. and Europe reveal that although the handshake and other types of physical contact have been on an extended hiatus, they are only gradually returning.
For example, research shows that contacts are less likely to involve physical touch now than before the pandemic and that masking remains common, the article said.
"When you ask people how many contacts did you have today or yesterday where you actually touched someone, you shook their hand or some other physical touch — that's actually a lower number than it was before the pandemic started," Nelson said.
However, Juliana Schroeder, an assistant professor in management of organizations at Berkeley Haas at University of California, who has done research on the gesture, suggested the handshake will likely be back in full form, because it's one of these memorable rituals to be transmitted through generations.
"That's why they have those ... physical features that are characterized by some repetition and some formality, some symbolism," she said.
"They're sort of easily ingrained. And so the handshake is definitely one of those. It's almost like second nature for people to stick out their hand when they see a new person."