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Prominent San Diego Scientists Argue COVID-19 Spreads Like Secondhand Smoke

 April 20, 2021 at 11:44 AM PDT

Speaker 1: 00:00 A new report in the medical journal, the Lancet says COVID 19 is spread primarily by small aerosol particles to San Diego. Researchers help make the case that the Corona virus has spread so efficiently because it is passed along by small aerosols that are released by breathing the researchers like in the aerosols to secondhand smoke. One of the report coauthors is Dr. Robert schooly and infectious disease specialist, and chief of the division of infectious diseases at UC San Diego health. He joins me now with more welcome, Dr. Schooley. So listen, one of the points you make in your paper is the difference between protecting yourself against a virus that spreads primarily through respiratory droplets and one that primarily spreads through aerosols. Will you explain those differences for me, Speaker 2: 00:50 We've had for a long time in infectious diseases, this construct that there are two different ways viruses and other pathogens are spread. One is by smaller aerosols that can travel for long distances. And the other is by large droplets kind of things you see in the air when you sneeze. These are big, uh, particles that fall to the ground. And about six feet. One of the misconceptions has been that because people who are closer to other people are more likely to get infected. This must mean that the virus is being transmitted in big droplets because the big droplets don't spread any further than that. Well, the small aerosols also are more concentrated. The closer you are to the source, they disperse. And as you get farther away, your likelihood of getting infected goes down. But that doesn't mean that you're not getting infected by these small particles when you're closed up. Speaker 2: 01:40 Now, why would this be important? Well, if there were only droplets and if droplets were the thing that actually carrying this virus, we wouldn't worry about being in closed rooms with people. Uh, we wouldn't worry about having, uh, somebody sitting across the table, six feet away eating a sandwich, because if these were droplets, they'd fall to the ground, they wouldn't reach. But in fact, these are the viruses and smaller particles that walked up in the air and can spread further than that. And that's why we recommend people wearing masks whenever they're indoors and, uh, using distance between themselves, because that allows both particles and aerosols to disperse as one more layer to protect them from SARS cov two. Speaker 1: 02:21 And talk about the evidence, uh, that you and your colleagues have gathered that supports the primary spread of COVID-19 through aerosols rather, rather than droplets. Speaker 2: 02:30 Well, there's some, there's some direct physical measurements looking at what particles the virus is most likely to be associated with. There's the smaller aerosols. There are several instances of, um, in which the virus has spread. For example, in choirs that can't be explained by direct droplets, uh, can only be explained by aerosol transmission. There are people who have gone into a room where someone has been, uh, and is no longer there, uh, who picked up the virus that can't be explained by, by droplet transmission. So, you know, our argument isn't that it has never spread about droplets, but that you also have to consider aerosols. When you are planning your prevention program. Speaker 1: 03:13 Now you and your colleagues have been sounding the alarm about the way COVID-19 is spread through aerosols for months. So why published this letter in the Lancet? Now, Speaker 2: 03:23 There's still quite a bit of resistance to wanting to refocus on this because it changes the way we approach the prevention efforts, both in hospitals and, and, uh, in the world, uh, we've seen, uh, outbreaks and places like the white house and other places where people say they were socially distanced and following the guidelines. But in fact, they weren't wearing masks and it's clear that those kinds of events, the ones we want to avoid, we still have the who that, uh, has, uh, been very slow to embrace the idea of, uh, aerosol transmission. One of the reasons they initially were, as they were concerned about alarming people. And, uh, they were also concerned that the, the logical conclusion of aerosol spread is people should be, should wear masks when they're around other people, there was a global mass shortage. And so the decided that this was transmitted by aerosol, so people should wear masks. They were concerned would lead to a shortage of masks in hospital settings from the public policy perspective. I think we're always better off saying, here's what we think the facts are from the public public policy perspective. Right now, we don't have a mass enough mass to have everyone in the world wear one, and they should be used preferentially in places of highest risk, but we shouldn't have the facts that are obvious tweaked to then make policy. Speaker 1: 04:44 Hmm. So we know that this virus has spread via aerosols is the N 95 or cloth mask as effective as a P 100 mask. Speaker 2: 04:53 There are gradations of effectiveness and probably the least effective as a gainer. Uh, then you start getting in to, uh, bandanas, and then you start moving up into masks that are made of multilayers of cotton, and that are tightly woven and then two and 90 fives. And then one hundreds. Now the virus is transmitted not to everybody. Every time you're in with someone it's, it's a, it's an issue of dose. And so each time you increase one of the things that prevents transmission, and it can be a better mask, more distance, not being endorsed, better ventilation of vaccine. Each one of those puts you at a better, uh, in a better position to avoid getting infected. So in situations in which a ventilation is difficult, a better master will be more important than, uh, when you're in places where viral concentrations are likely to be lower. So it's just one of the many things that we try to optimize when we're trying to prevent spread of the virus while we hope that more and more people become and Speaker 1: 05:59 You and, and other scientists have been calling on the CDC and the world health organization for months now to update their guidance on how people should protect themselves from COVID-19 infection, what harm is being caused by not changing their recommendations for protections against COVID-19. Speaker 2: 06:15 The major harm is, is it puts people in positions that, um, they may get infected. That that has several implications. First of all, true, many of the people are getting infected now are younger people who are less likely to get sick, but some of them do get sick. Uh, secondly, there are older people who may have underlying immunodeficiencies that may get vaccinated, trying to protect themselves, but the vaccine may not induce immunity because they're on an immunosuppressive drug. So people who are, uh, not taking into account their own aerosols, but those people at risk, uh, who are doing the best, they can not to get infected and get sick. And thirdly, uh, but not paying attention to aerosol transmission, allowing the virus to, uh, to, uh, spread we're allowing the virus to develop more and more, um, difficult variants that are going to be harder and harder to control by vaccines and ultimately making it harder to control the epidemic. So focusing on aerosol transmission and ways to prevent that while we're working on getting vaccine immunity is a very important, short and long-term goal. Speaker 1: 07:18 I've been speaking to Dr. Robert schooly and infectious disease specialist, and chief of the division of infectious diseases at UC San Diego health. Thank you very much for joining us. Speaker 2: 07:28 Welcome. Have a good day.

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Two San Diego researchers hope a new peer-reviewed article helps them convince federal officials to change their opinion of how COVID-19 spreads.
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