Norman Swan: Hello, this is Coronacast, a podcast all about the novel coronavirus. I'm physician and journalist Dr Norman Swan.

Tegan Taylor: And I'm health reporter Tegan Taylor, it's Friday, 17 April.

So today, let's just jump straight into questions. And Norman, I have some really good ones for you, including a personal favourite of mine; can the coronavirus be transmitted through farts? Let's get into it.

Philip is asking whether Australia is making preparations to eliminate rather than control the virus like New Zealand.

Norman Swan: The answer is mixed. It depends on who you talk to. It's clear that some of the states in Australia are heading for elimination, even though they might not be talking about it explicitly. So South Australia, Western Australia, even Tasmania. If they hadn't had that cluster in Bernie in north-western Tasmania, they would be pretty close to zero cases. And what you need is zero cases day after day, probably for at least 14 days, if not a month as you go through two different cycles, with massive testing of the virus. Some states are pretty close to that. New South Wales, Victoria, Queensland, a little bit further away. We could be heading for that, and the states might be ahead of the Commonwealth on that. Because you can't really let your foot off the brake until we've driven this down to very low levels, and in theory we could eliminate it entirely. We've eliminated animal diseases from Australia, like foot-and-mouth disease, and there are far more farm animals in Australia than human beings, and they don't socially isolate. So I think that we can actually eliminate this virus from Australia, and when we do and we keep our borders closed, we could actually get to a more rapid release of controls and social distancing. But the Commonwealth is being a bit coy about whether they are heading in that direction.

Tegan Taylor: Why do you think the Commonwealth is being coy about this?

Norman Swan: I've got no insight into that. The Commonwealth throughout this has been a little bit behind the states in terms of assertion and aggression and going after this virus. Although, to its credit, they are resisting strongly the lobbying at the moment to lift off the controls, so that's a good thing. I think there are people in the Commonwealth who don't believe that elimination is possible, I think that's the basic thing, and the modellers that they've used at the Doherty Institute in Melbourne, those modellers don't believe that elimination is possible, whereas other modellers in Australia do believe it's possible. So I think it's partly the people they are listening to.

Tegan Taylor: Is that just something that we will never really know who was right until after the fact?

Norman Swan: Well, in New Zealand they are down to single digit numbers the last time I looked. They are probably going to get there by the end of the month, beginning of May. So why wouldn't you go for this? We are almost at complete lockdown in Australia, apart from schools. We've asked a lot of people why would you let up the brakes when the prospect is you could actually eliminate the virus from the country. Now, the people who say, oh no, that's not possible, they revert to the whole thing about there's all this coronavirus around Australia, but if our borders are blocked, nobody is coming in, then we can, and it's just a question of when we lift international controls, and that might not be for many, many months to come.

Tegan Taylor: Well, talking about the Commonwealth, we've actually got the Deputy Chief Medical Officer Paul Kelly coming into talk to us next week, we're going to be putting your questions to him. So if you've got a question for Professor Kelly, send it in, go to abc.net.au/coronavirus and fill in the form. Make sure you use the word Coronacast so that we can find it.

Norman Swan: And no doubt one or two of them will be about elimination.

Tegan Taylor: We've got a question from Ian asking whether if you're a young or middle-aged person, you've got mild symptoms, you're positive for COVID-19 and you are in isolation at home but if your symptoms start getting worse (we were talking the other day about that second-week crash), what signs should people look out for as a sign that they need to go to hospital?

Norman Swan: If you get better, you start to feel okay, and then you get worse again, your cough gets worse, you're feeling breathless, people look at you and say you're looking really unwell, you're a bit blotchy…I don't know if people remember the video that Boris Johnson put out two or three days before he ended up in intensive care, he was at home, he looked terrible. So your blood oxygen levels are going to drop, so you're going to look a bit blueish and blotchy and just not well. Hopefully you don't get that far.

But I think that if that day 5 to 7, 8, you are feeling that you're getting worse again, I think that's when you check in with your GP and start to think about getting checked up. What they'll probably do is a chest x-ray or a CT scan maybe, and also check your blood oxygen levels because blood oxygen levels tend to drop as well. Look, if at any time if you're worried you should talk to your GP, but if you go through a period where it seems okay and then around about a week later you seem to be falling off the cliff, you don't delay, you talk to your GP who will probably send you in to the emergency department.

Tegan Taylor: We've got a question about what can kill the virus, we've got lots of questions about what can kill the virus, but specifically microwaves. Could you microwave masks, cloth gloves and sponges et cetera as a way to sterilise them?

Norman Swan: I have not seen any studies of microwaving. The microwaving would have to heat the virus to reasonably high temperatures to actually have an effect in the penetration. I think that the penetration of what you're microwaving is the issue, whether that's even, and you probably won't know it. And if you can put it in the wash, why wouldn't you, because putting it in the wash with laundry detergent is going to kill the virus, you know that, it's going to penetrate all the surfaces, why would you take a risk with microwaving?

Tegan Taylor: A final question from an audience member for you today, this is David with a hard-hitting question; if the virus can turn up in faeces, does that mean that farts could be a transmission route?

Norman Swan: You get really intelligent, pointed questions on Coronacast and this is no doubt one of them. Well, luckily we wear a mask which covers our farts all the time, so I think that even if it were to…I think that what we should do in terms of social distancing and being safe is that a policy on the part of the entire Australian population should be that you don't fart close to other people, and that you don't fart with your bottom bare.

Tegan Taylor: This is excellent advice from Dr Swan. Thank you so much for clearing that up.

Norman Swan: Yep, science-based, this is hard-core evidence here we're talking about.

Tegan Taylor: No bare bottoms.

Norman Swan: No bare-bottom farting.

Tegan Taylor: So one of the things we do on most episodes of Coronacast is talk about a piece of research and that's what we're going to do today. And we've got one that you want to talk about, Norman, about when people are most infectious.

Norman Swan: Yes, this is a study which comes from China, looking at the shedding of virus. It's fine to say that you've got the virus on board, but are you actually losing the virus into the atmosphere and spreading it to other people? And they did a study in China of about 77 pairs of people who…they knew the transmission path. Just under half of people spread the virus, they were shedding the virus prior to when they were symptomatic, in the pre-symptomatic stages. So it confirms what we know, and we've already had one question today acknowledging that, is that the asymptomatic spread is very significant in COVID-19. And so although this comes from earlier on in the epidemic, we are keeping on getting…in science the more reproducibility you get of results, the more confident that you can be. So we were saying maybe two or three weeks ago, four weeks ago it was 50% asymptomatic, that came from Korea I think initially. And now we know from a very specific study really looking at virus shedding that it is around the 40% to 50% range, which means that asymptomatic spread is significant and it's why people are starting again to talk about masks so that asymptomatic people don't spread it in public, and that we are careful with social distancing because you don't know who you're coming in contact with.

Tegan Taylor: One of the things I found really interesting about this study was it compared SARS-CoV-2 to the original SARS which…you were most infectious with SARS several days into having lots of symptoms, so that made it relatively easy to lock that virus down, whereas this is transmitting before people have symptoms, and so it's really hard to get a handle on that when people haven't even shown that they are sick yet.

Norman Swan: That's right. I think it was day two or something like that with SARS-1, it was where you really began to be infectious and then continue from there. So even if you got somebody in the door and they said, look, I've just got symptoms from last night, you had some time here, and then you knew exactly…and that's why healthcare workers were so much at risk because largely it was healthcare workers who came in contact with these people when they were symptomatic.

Asymptomatic here changes the nature of it, and this is why we are going to have to accept…even if we got to elimination and we started to lift controls, we are going to have to check everybody with a cough and a cold. And you say, well, why would you do that when 50% is asymptomatic? The only way to find asymptomatic people really systematically is find everybody with a cough and a cold, test them, and there'll be a very small number who are COVID-19 positive, so do tens of thousands of tests for one or two positives. But for those one or two positives we find everybody they've come in contact with, whether we use one of these tracing apps or traditional contact tracing. And those contacts are potentially the people who will have asymptomatic spread because you know when they came in contact with them, you know what the average incubation period is and you can either test them or you can put them into strict quarantine and test them as you go along.

But that's how you prevent asymptomatic spread, is find people with cases, find the people they've come in contact with. You always miss one or two people who are asymptomatic in the community, but you'll get most of them. Isolate the person with COVID-19, strictly quarantine the people they come in contact with, testing, and then you'll start to really get a handle on asymptomatic spread.

Tegan Taylor: Well, that's all we've got time for in Coronacast today, but, as a reminder, Paul Kelly the Deputy Chief Medical Officer is coming to speak to us next week. Send us your questions for him by going to abc.net.au/coronavirus, and make sure you use the word Coronacast in your questions so that we can find it.

Norman Swan: And if you like the show, give us a rating and please review us at Apple Podcasts, we really like reading them and it helps others find us. Tell a friend about us too, you can find us at Apple Podcasts, you can find us on Spotify and Google Podcasts, as well as the ABC Listen app. We'll see you on Monday.

Tegan Taylor: See you then.