Coronavirus: Warning over aerosol risks, tracking SARS-CoV-2 in social media and sewage, repurposing common medications for COVID-19, and evidence based help for your mental health

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Health Report 28 min 2 speakers 5 chapters transcribed 3 days ago

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What is the main topic discussed in this episode?

Unknown 0:01

This is an ABC podcast.

Dr. Norman Swan 0:06

Hello and welcome to this week's health report with me, Norman Swan. Today, what coping strategies have we been using during the COVID-19 pandemic and what's the evidence for and against? Victorians in particular should listen. Two new COVID treatment trials coming out of Australia using cardiac medications. getting closer to patient zero in China and an open letter from over 230 scientists which has received a lot of coverage and it argues that we've underestimated the role of airborne transmission, primarily aerosols, in the spread of the COVID-19 virus and as a consequence we need to address a wider range of control measures. What we're talking about here are so-called micro droplets. Unlike bigger droplets, which have been the focus of the WHO and indeed our own government in terms of physical distancing, hand washing and concern about contaminated surfaces, micro droplets are produced when we speak, sing, laugh, cough or sneeze and can travel many metres in seconds and linger in the air sometimes for hours.

Dr. Norman Swan 1:02

Aerosols have been blamed for spread in restaurants, some home spread and at least one infamous choir practice in the United States. And physical distancing or indeed hand washing doesn't help. One of the letter's two primary authors is Linda Morowska, who's professor of atmospheric scientists and environmental engineering at Queensland University of Technology. Welcome to the Health Report, Lydia.

Lidia Morawska 1:24

Good evening. Thanks for inviting me to the report.

Dr. Norman Swan 1:27

What evidence do you have that aerosol spread with COVID-19 virus is so important?

Lidia Morawska 1:32

Well, we've studied this for four years and we know very well when we, as you said, when we speak, breathe, cough and so on, we generate these micro droplets, aerosols of different sizes. If we are infected, they contain a virus or the virus, depending on what infection it is. If they are small enough, they can linger in the air for some periods of time. And if others share the same indoor environment, they can inhale them and be infected.

Dr. Norman Swan 2:03

How do they linger in the air? Because it seems counterintuitive. Even if they're micro droplets, you'd think that gravity is going to take them to the ground pretty soon.

What is the new evidence that aerosol transmission drives COVID‑19 spread?

Lidia Morawska 2:12

Well, gravity really takes the bigger droplets. So occasionally when we talk to somebody who is very excited, we see big droplets coming. And these droplets are of the size of a millimetre or so. Then gravity takes droplets like this very quickly. But when we are talking about something of the size of several micrometres, they are light enough that gravity is not the only force affecting them. Think of many currents in the air. These currents could be a more important force for keeping them in the air than the gravity.

Dr. Norman Swan 2:44

Can you give me examples of where you think aerosols have been responsible for transmission?

Lidia Morawska 2:51

Well, we've studied retrospectively infections from the choir practice, for example, the one in the United States at the beginning of the pandemic. By that stage, the participants of this event already knew about the procedures which needed to be taken against the spread.

Dr. Norman Swan 3:10

Yeah, there was nobody with symptoms there and they were physically

Lidia Morawska 3:13

distanced. They were not touching, not sharing everything. That's right, yeah. So what was the reason? Our investigations shown that the only logical explanation to this is that this was airborne spread. The same in a restaurant in Guangzhou. Again, this is the only explanation what happened there and many other events like this.

Dr. Norman Swan 3:34

And, you know, if you take the spread of sort of our government, the WHO focuses on physical distancing, hand washing and so on, which is about large droplets spread. What's the guess that the contribution that aerosol spreads make, aerosol spread makes to the spread of COVID-19?

Lidia Morawska 3:55

Well, everybody asks this question, what is the proportion? It really depends on the environment. If we are talking about an environment with very good ventilation, the virus is removed from the air very quickly and then airborne transmission is of no significance. However, if ventilation is not efficient, then this is the main mode of transmission.