We know that we can get the coronavirus by breathing in respiratory droplets exhaled, coughed or sneezed by someone with the disease.
So does it help to hold your breath when you pass mask-free strangers on the street, or when you have to share a public bathroom, or crowd into an elevator with other people?
"I've done about 750 national and international interviews now" on the COVID-19 pandemic, said Dr. Gregory Poland, a Mayo Clinic professor of medicine and infectious diseases and director of the Mayo Clinic's vaccine research group. "Nobody has asked me that one."
But Poland's response: Why not?
"If you're not breathing in, you've dramatically cut down the risk logically," he said.
In fact, he said he and his family hold their breath during brief encounters with other people.
"When we're going by people and you have to be unavoidably close, hold your breath," he said. "You have reduced the risk of breathing it in at no cost."
Dr. James Johnson, a University of Minnesota Medical School professor specializing in infectious diseases, also said holding your breath can make sense in some situations.
"Part of the risk of catching the virus is from what's in the air when you inhale. So if you can avoid inhaling while in a high-risk micro-environment (elevator, vicinity of somebody who coughs or sneezes), sure why not," Johnson wrote in an e-mail.
It's already something many of us have been doing.
Jason Larson, a triathlete, trail runner and stair climb racer from Golden Valley, said when he encounters someone else while on training runs, "I adjust my breathing so I'm not inhaling when I'm downwind of someone."
Scott Otey also has been holding his breath when he gets near other people in the grocery store. And he can do it for minutes on end. The Janesville, Wis., man is a spear gun hunter and free diver who dives underwater without scuba gear.
He teaches other people free diving, and he said with a little training most people can hold their breath for longer than they think.
"In an elevator, when you're not moving, you can probably do two minutes," he said. "Anybody can do it."
Both Johnson and Poland, however, said holding your breath should not be a substitute for the primary tools we have to avoid spreading the virus: social distancing, hand washing and mask wearing.
You may avoid breathing in the virus if you hold your breath when someone coughs near you, but if virus-laden droplets land on your body or clothing and you touch them with your hands and then touch your nose, mouth or eyes, you still may get sick.
Poland also cautioned that holding your breath may be counterproductive in some situations.
If you're close to others and can't hold your breath long enough to move away, you'll typically exhale forcefully when you have to start breathing again.
If you're infected and don't know it, "you have now spread that virus for about 30 feet around you," Poland said.
Or you'll take a deep breath in, which defeats the purpose if you're still near the people you were trying to avoid.
Breathe right
When you breathe, at least breathe through your nose, urges Louis Ignarro.
Ignarro is a pharmacologist who got his doctoral degree at the University of Minnesota. He became a co-recipient of the 1998 Nobel Prize in physiology or medicine for his research on nitric oxide, a gaseous molecule that causes blood vessels to relax and widen.
Ignarro's research into nitric oxide led to advances ranging from the Viagra pill to treatments for premature babies with failing lungs.
In addition to improving lung function, nitric oxide (which should not be mistaken for nitrous oxide, commonly known as laughing gas) has antiviral and antibacterial properties.
Now researchers are conducting studies to see if inhaling doses of nitric oxide gas can be used to treat people with coronavirus or even prevent health care workers from getting the disease.
We also naturally generate nitric oxide in our nasal passages when we breathe in through the nose.
So Ignarro has recently been writing articles urging everyone to inhale through the nose during the pandemic.
"It's good to breathe through the nose, not the mouth, because then you're going to get that nitric oxide into the lungs," said Ignarro, a retired professor from the UCLA School of Medicine.
Johnson said that breathing through the nose can filter out particles and keep them from getting into the lungs.
"The problem here is that [COVID-19] multiplies quite nicely in the lining cells of the nose and upper throat, so it may not need to get to the lung initially to establish a 'foothold,' " according to Johnson.
Ignarro admitted there isn't scientific proof that breathing through your nose will ward off COVID-19, and people should still be taking other precautions. But he said it can't hurt to try breathing through the nose behind your face mask.
"It's a logical guess," he said. "If you don't have the virus and you breathe in through the nose, you just might be able to prevent that coronavirus from settling down in the lungs."
And breathing through the nose is a good idea generally, according to James Nestor, a journalist who just wrote a book about breathing practices called "Breath: The New Science of a Lost Art."
According to Nestor, the nose "filters air and gets rid of particulate. It conditions it and humidifies it so that air that enters the lung from the nose is so much easier to process for the lungs."
Humming along
But to really increase nitric oxide, Nestor suggests humming.
Studies have shown that nasal nitric oxide can be increased 15-fold by humming compared with normal, quiet breathing.
Even before the COVID-19 pandemic hit, some health practitioners were touting the benefits of humming to improve conditions like sinus infections or the common cold.
Nestor said if he encountered someone coughing on the streets of San Francisco where he lives and he couldn't get out of the way, "I would hum," he said. "Not only are you increasing that nitric oxide, you're also slightly exhaling," rather than breathing in.
"People are going to call this quackery or pseudoscience," Nestor said.
But unless you hum so much that you get dizzy, what's the downside?
"People are going to look at you and think you're a weirdo, but that's fine. Hum on by," Nestor said.
