Donald Milton on Aerosol Transmission of COVID-19

[ad_1]

One of the reasons Covid-19 is spreading so fast, which is infecting many people around the world, is that researchers initially struggle to understand exactly how it is transmitted. They eventually decided that it could be spread by inhaling small droplets, known as aerosols, that those infected with the virus inhale. But even with that knowledge, there is an additional challenge in getting various health authorities, including the World Health Organization and the Centers for Disease Control and Prevention, to communicate the risks to the population in general, and for governments. to establish public health policies accordingly. .

Donald Milton, an aerosol expert at the University of Maryland School of Public Health, is on the front line of this struggle. Last summer, he co-authored an open letter to the “medical community and to relevant national and international bodies,” including the WHO, published in the journal Clinical Infectious Diseases, signed by 239 health professionals from 32 countries.

The letter won home to the point that Covid-19 spread not only macroscopic droplet types produced by coughing, sneezing, talking, or singing nearby, and quickly fell to the ground but to by microscopic droplets that can be suspended in the air for extended periods and travel further. Only by understanding this mechanism of transmission can the right steps be taken to slow the spread of the disease, Milton and his colleagues argued.

In a recent Zoom conversation and email exchange, Milton discussed his research into aerosol transmission of respiratory viruses, his early campaign to warn health agencies that Covid-19 was in the air and its effects, and what we can do to better prepare for the next pandemic. . Our interview was edited for length and clarity.

Undark: It was more than a year ago that you co-authored that commentary article on Clinical Infectious Diseases arguing that the risk of airborne transmission with Covid-19 was underestimated. What led you to take that course of action?

Donald Milton: It’s been a concern from the very beginning, that aerosol inhalation could be important to this respiratory virus. The pandemic raged through a first wave, and there will clearly be subsequent waves. Our research has shown that you can do a lot to limit the spread, if you take it to the head first. But you have to acknowledge it, you have to face it. And it doesn’t happen to WHO especially. And the CDC is kind of saying “good, maybe” and urging caution; but neither do they send a clear message.

UD: Did the article have the impact you expected?

DM: Finally, I guess. The CDC and the WHO have recently, in the last few months, made stronger statements about the role of inhalation exposure. But it took a long time; it did not happen overnight. The CDC has never denied; just take before putting [recognition of the airborne transmission risk of Covid-19] at the top of the list. When the work goes into the books over the next few years and is taught in medical schools and the older generation retires, it will be part of the overall toolbox of trainees.

UD: Many health authorities seem to be committed to the 6-foot (2-meter) rule as if it offers some sort of full protection. Did it go wrong?

DM: It goes back to this parking lot of droplets-versus-aerosols. There is a belief that everything is not TB [tuberculosis] needs to be droplet-sprayed; and that the spray is not very far. Not understanding that it is inhalation, and there are many things larger than desirable aerosols that can be deposited in your nose, and in your large airways; and if there are susceptible cells, it can cause infection; and can still hang in the air. That’s the paradigm that really needs to disappear.

UD: In the first few months of the pandemic, a lot of emphasis was placed on disinfected surfaces. We’ve heard that grocery stores are wiping their shelves, carts, and baskets and that New York is scrubbing down cars on its subway. But at the same time, messaging with masks is often confusing.

DM: In the beginning, think very carefully about all the delivery routes. The CDC recommends both decontamination and staying behind 6 feet, and recommends wearing N95 masks when you talk to Covid patients. And they are right; their problem is, they said, “If you don’t have N95 masks, you can do other things” which usually gives passage to hospital administrators who aren’t ready yet.

UD: Initially, there was a lot of debate about the issue of how much protection masks do, or don’t, provide. What has your own research shown?

DM: I’ve been looking at it since 2007. We developed a device to measure how much virus is shed by people wearing masks, and by people not wearing masks. We published a paper [in 2013] showed that the masks reduced a bit of what people poured but they did not remove it, because the masks were often loose, and fine-particle aerosols could still come out. But it reduces fine-particle aerosols by a little over 50 percent, and it reduces large droplets, and coarse aerosols, even more.

UD: Should there be more emphasis on ventilation?

DM: If you don’t recognize aerosol inhalation as a route of delivery, you won’t think about ventilation. So it’s very noticeable. And that became part of the importance of our letter.

UD: Of course, getting science right is just the first step. Can you say something about the challenge of delivering science to the public especially to a public that may, in some cases, not trust authority?

DM: One of the critical things to say is: “This is an evolving situation, and we don’t know everything yet. This is our best understanding so far. Here’s the best thing we think you can do. . ” And tomorrow you say, “We learned something new, and we changed our recommendations. ” But it’s really hard to do that. I think in medicine, we’re likely to come across as,” We know what’s going on; here’s what you should do. ”But it can come back if in fact you don’t really know yet. That’s why it’s so important to be straightforward about what you know and what you don’t know, what you’ve learned, and what are you doing to find out.

The problem of course is that being frank about what you don’t know will lead to some people not doing what you recommend. But I think in the long run, you’ll end up with a lot of people doing what they need to do, as opposed to if you’re confident and then your credibility is destroyed and then no one listens to you after that.

UD: How confident are you that the lessons of Covid-19 are being absorbed, and that the next pandemic will be better handled?

DM: I don’t know. I think there is clear evidence that Taiwan and South Korea, and perhaps Vietnam, have learned lessons from SARS: They understand the warning shot; they paid attention and they did a bit better than most anywhere else. If [the next pandemic] will come over the next 10 to 15 years, I think there is a good chance that the memory of life will serve us well.

UD: What can we do to be better prepared?

DM: I think we need to invest in two pieces of infrastructure, to make sure we can respond better. The first is research infrastructure. There has been no way clinical medicine studies, particularly randomized control trials, of the route of transmission of respiratory viruses. We need the gold standard of evidence, to get everyone on the same page. And that is an investment not only in research studies, but also in research facilities.

And the second part is, we need to make our public spaces more resilient and more stable, and less allow for delivery. Some of that goes down to ventilation, which can be far -fetched, especially in the early stages of a pandemic. If we really had effective air sanitization in schools and restaurants and other places where people gather, you could prevent most delivery. And then you don’t have to shut down the economy when you have a pandemic virus.

You just tell people to mask. And respirator stockpiles, for hospitals. I think the lessons are there to be learned, and a lot of people are learning from them. The question is, are we willing to invest in the protection we need. That is always a question. My parents ’generation built the DC subway; in my generation, we hardly produce a light rail line.

Dan Falk (@danfalk) is a science journalist based in Toronto. His books include “The Science of Shakespeare” and “In Search of Time.”

[ad_2]