The virus that causes COVID-19 could be a lot easier to spread than many people realize.
It might even be possible to give somebody the SARS-CoV-2 virus by simply talking to them, a team of scientists concluded.
That’s the bad news. The good news is that masks could help limit that spread. Possibly a lot.
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“The act of speaking generates oral fluid droplets that vary widely in size, and these droplets can harbor infectious virus particles,” Philip Anfinrud, Valentyn Stadnytskyi, and Adriaan Bax at the National Institutes of Health in Bethesda, Maryland, and Christina Bax at the University of Pennsylvania wrote in The New England Journal of Medicine.
That spit from our speech could spread a virus should surprise no one. There’s not a whole lot of difference between a cough and a shout, after all, as other studies have revealed. “Our research and technology-development already has this presumption built in,” Herek Clack, a University of Michigan engineer working on new medical masks, told The Daily Beast.
But Anfinrud, Stadnytskyi, Bax, and Bax’s experiment underscores just how easily, and how far, our words could project a virus like SARS-CoV-2. The study could have huge implications as some Americans grow impatient with social distancing and, encouraged by President Donald Trump and his allies, clamor for an end to public health measures.
To quantify the amount of spittle in our speech, the scientists cobbled together a combination of high and low technology. They took a cardboard tube, painted it black, cut a slit three inches from the opening, and shined a green laser through that slit.
The laser created a “sheet” of green light that sparkled whenever a particle passed through it. The scientists had test subjects say, through the open end of the tube, the words “stay healthy”—and rigged up an iPhone to record high-resolution video of their spittle sparkling in the laser.
The testers counted the sparkles and measured their intensity in order to get a sense of how much, and how far, talking can spread virus-laden spittle. Speaking loudly produced as many as 347 measurable droplets in a single frame of the video. Dropping to a loud whisper reduced the droplet count as low as 227.
Each of those droplets could transport pathogens.
But Anfinrud, Stadnytskyi, Bax, and Bax didn’t try to estimate how great a viral load the words “stay healthy” might carry. “Our aim was to provide visual evidence of speech-generated droplets,” they wrote.
And it’s almost certain that the scientists’ count is on the low end. Very fine “aerosolized” spittle probably wouldn’t set off the laser detector, Harvard molecular biologist Matthew Meselson explained in a letter to The New England Journal of Medicine. “The diameters of these particles are in the micron range,” Meselson wrote. “These particles are too small to settle because of gravity, but they are carried by air currents and dispersed by diffusion and air turbulence.”
Just how much virus can ride along in very fine spittle remains the subject of urgent study. “It remains an open question how important this is in COVID-19 transmission,” Keith Jerome, director of the University of Washington Virology Lab, told The Daily Beast. “Does this explain why there’s such easy spread, or is it just a minor contributor?”
“Until we have that level of information, it is difficult to know the efficiency of transmission through these expelled aerosols,” Seema Lakdawala, a molecular geneticist at the University of Pittsburgh School of Medicine, told The Daily Beast.
Don’t panic. Yes, our words might spread the coronavirus. But that doesn’t necessarily mean we need to stop having face-to-face conversations.
Anfinrud, Stadnytskyi, Bax, and Bax had some of their test subjects speak through a damp washcloth standing in for a medical-style mask. That all but eliminated the spittle. “The flash count remained close to the background level,” the scientists wrote.
Taken as a whole, the laser experiment is a reminder of “the advisability of wearing a suitable mask whenever it is thought that infected persons may be nearby and of providing adequate ventilation of enclosed spaces where such persons are known to be or may recently have been,” Meselson wrote.
As for what qualifies as “suitable,” Clack is clear. We need better masks. “There is a need to develop better protection against infectious agents in air, and that need is all the more acute when vaccines are either not available or are limited in their effectiveness.”
