Can loud talking spread coronavirus?

There’s still a lot we don’t know about Covid-19, but one thing is certain: It spreads like wildfire. The global tally now stands at more than 10.7 million infected, although the World Health Organization believes the true number is much higher, with one estimate stating 5 per cent to 8 per cent of the population has been infected.

One of the most important things to understand about the virus is how it spreads. Just like the flu, the new coronavirus can spread via sneezing and coughing. But some experts also worry that you can catch Covid-19 from someone talking, singing, shouting, or even just breathing heavily. “All the research is very, very new,” says Dr Teresa Murray Amato, an emergency medicine specialist. “We’re learning how to fly the plane while building it at the same time.”

Here’s what we know so far about how the virus itself flies—literally—between people and whether talking, especially loudly, to others, can really increase the risk of infection.

At the most basic level, experts believe that Covid-19 passes primarily between people who are in close contact with each other. As a respiratory virus, it lodges in the back of the throat and behind the nose then burrows into the bronchial tubes which lead to the lungs, explains Dr William Schaffner, an infectious disease specialist. A cough or sneeze from an infected person propels the virus, which hitches itself to respiratory droplets, into the air. Covid-19 is most easily transmitted when two people are within 1.8 metres of each other and inside, even if a person has no symptoms, a March 2020 study in Science China Life Sciences shows. Touching a contaminated surface then touching your eyes, nose or mouth can also spread the virus, though probably not as much. “To the best of our knowledge, these are the only two ways you can get infected with the virus,” says Dr Greg Poland, an expert with the Infectious Diseases Society of America (IDSA).

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Experts are now trying to figure out whether the virus spreads through respiratory droplets alone, or respiratory and aerosolized droplets. What’s the difference? Respiratory droplets are bigger and heavier than aerosolized particles so gravity pulls them earthward quickly, minimizing the time you could be exposed. Aerosolized particles, on the other hand, are smaller and lighter and float around for longer and travel farther, making them potentially infectious for longer, according to a March 2020 study in the New England Journal of Medicine (NEJM).

“Think of it as a sliding scale based on droplet size,” says Dr Poland, who is also a professor of medicine and infectious diseases at the Mayo Clinic, director of the Mayo Vaccine Research Group and editor-in-chief of the journal Vaccine. “The larger the droplet, like if I cough or sneeze, those generally fall out of the air in about 1.8 m to 3 m or less. Models show that aerosolized particles will spread in a cloud of about eight metres and linger in the air not for a minute or two but for 30 minutes or so.” An April 2020 NEJM study recorded that SARS-CoV-2 (the virus that causes Covid-19) aerosol bits stayed viable in the air for three hours, although its infectiousness did decrease.

We know that coughing and sneezing can transmit the Covid-19 virus, but can talking also launch the virus into space? Possibly but, like so many other things around Covid-19, we don’t know for sure, says IDSA spokesperson Ravina Kullar, a doctor of pharmacy. Researchers publishing in the Proceedings of the National Academies of Sciences (PNAS) used laser light scattering to picture particles produced when a person uttered “Stay healthy,” at three different volumes. Droplets were expelled at all three volumes, but the louder the person spoke, the more particles they emitted and the greater the spread.

What’s more, the droplets stayed in the air for anywhere from three to 14 minutes, points out Dr Kullar. What we don’t know is whether all those droplets from speech actually translate to infectious risk, she points out. People who enter a room after someone with measles has occupied the space can still get sick. That’s because the aerosol particles linger in the air. “We’re not seeing the same story for SARS-CoV-2,” she adds. “That’s what’s making scientists wonder is it a respiratory or aerosol phenomenon.”

The PNAS study reported that covering the face with a damp washcloth effectively prevented the particles from escaping.

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Talking (especially talking loudly) and singing along with cheering, chanting, and yelling are all variations on the same theme, points out Dr Schaffner, who has fielded calls from music teachers wondering if they can resume choral singing classes. “It’s pretty standard stuff,” he says. “When you’re yelling or singing, obviously you’re exhaling with more vigour, giving it literal energy, and you’re throwing your exhalation out a greater distance and literally bringing up more virus.”

There is plenty of research suggesting that singing can, indeed, spread the virus. One of the earliest examples was that of an American choir practice. Sixty-one people practiced together on March 17 for two-and-a-half hours. One infected person with symptoms infected at least 32 individuals; another 20 people may have also contracted Covid-19 from this person. Three went into the hospital, two died.

Experts are also concerned about contact sports: “You’re breathing deeply and you’re close to each other,” says Dr Kullar.

All evidence so far points to being safer outdoors. “The virus spreads most easily if you’re together for prolonged periods of time in an enclosed space,” says Dr Schaffner. “If you’re outdoors and the breezes are blowing, there’s more dilution and it doesn’t spread as readily. The vast amount of transmission occurs within a space of six feet [1.8 metres].”

Other outdoor environmental factors also play into it. Higher temperatures and vapour pressure along with UV light and are bad for the virus, good for you. In general, the higher the temperature, the shorter the “life” span of the virus, explains Dr Poland, although viruses aren’t technically alive.

One reason why experts are less concerned about the Black Lives Matter protests contributing to infections is that the events have taken place mostly outdoors. One American study conducted by the National Bureau of Economic Research, that analysed June 2020 mobile-phone data confirmed no spikes had, as of June 30, been recorded among local protestors. The authors speculate that this was due at least partly to more people staying at home after the protests. “We do think that the outdoors gives you some sort of protection but that’s no guarantee,” says Dr Murray Amato.

As the previously mentioned PNAS study shows, wearing a face covering is important. “It’s able to capture some of those particles and block them from being transmitted,” says Dr Kullar. According to Stanford University, respiratory droplets, which are larger, evaporate into the smaller aerosolized particles. Masks catch the droplets before they evaporate and become potentially more dangerous particles.

In America, mask-wearing is also recommended by the Center for Disease Control, especially in tight spaces and larger crowds. A June 2020 study in Health Affairs found that mask-wearing in 15 American states where it was mandated prevented as many as 230,000 to 450,000 Covid-19 cases.

“Viruses use human nature and human nature is to be together,” says Dr Murray Amato. “We have to find ways to trick or outsmart the virus. Right now, we don’t have a cure. The only thing we can really do is modify our behaviour.

Stanford University recommends not sharing your face mask and keeping it protected when you’re not using it (maybe in a Ziploc bag). “Charging your mask may also make it more effective.” Stanford scientists rubbed different types of fabric—cotton, polyester, polypropylene, nylon, and silk—with latex gloves for 30 seconds and found that this increased their protection by as much as 30 per cent for several hours.

The question of whether the Covid-19 virus can spread through aerosolized particles is still in the realm of the theoretical. For now, advises Dr Schaffner, focus on what’s important—which is that Sars-CoV-2 can spread through respiratory droplets. And wearing masks will minimize that risk.

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Source: RD.com