Norman Swan: Hello, this is Coronacast, the podcast all about the coronavirus where we answer your questions. I'm physician and journalist Dr Norman Swan.

Tegan Taylor: And I'm health reporter Tegan Taylor. It's Tuesday, 7 April.

So, Donald Trump, the American president, has been talking a lot about a certain drug called hydroxychloroquine. It's an old malarial, it's sometimes used to treat autoimmune diseases. Norman, why is it getting so much hype around COVID-19?

Norman Swan: Because President Trump and Peter Navarro who works with him as one of his economics advisers are convinced that it's the magic formula for treating COVID-19. There are anecdotes from around the world that it may have helped people. It's an optional extra, even on the Yale University guideline for the treatment of COVID-19, but in the context of a trial. And it's been a source of conflict between President Trump and his senior adviser or one of his two senior advisors, Tony Fauci from the National Institute of Allergy and Infectious Disease who has really been saying, well, we need a randomised trial here, and keeps on saying that but Donald Trump has supposedly stockpiled millions of doses of hydroxychloroquine. So everybody is getting very excited, and quite likely they are getting excited over nothing.

Tegan Taylor: What's the implication when certain drugs get politicised like this?

Norman Swan: Well, what happens is they get picked up and used because people somehow think it's got an imprimatur. So you've got people buying hydroxychloroquine, taking it prophylactically thinking it's going to protect them against COVID-19. These drugs have side effects, they are not necessarily entirely safe, and you've just got to be careful. And then by just taking them blind, you're stopping the option of a clinical trial taking place where you can actually decide whether it's effective or not. Because the other thing that could happen here is that it might be effective, but it has a low what's called effect size. Because you don't have the chance to do a proper trial, you actually might throw hydroxychloroquine in the bin, saying it's not effective, whereas if you had a large enough trial that's well enough designed, you might pick up a significant effect size that just casual use would not pick up. So there's lots of reasons not to do it, not to start it. Just be patient.

Tegan Taylor: Just one more question. We do know that hydroxychloroquine in large doses can be toxic, so what is the evidence so far, broadly, on its use for COVID-19, do we know?

Norman Swan: It's purely anecdotal. I think that in some parts of the world it has been used and they think it's been associated with a more rapid recovery, but it's been in an uncontrolled environment or if it has been in a controlled environment, some very low numbers where you can get aberrant results. It's just all over the shop. There is a signal there that it may have an effect. It's certainly worth studying. I go right back to the AIDS epidemic, when AIDS started off there were all sorts of mad stuff being suggested, people trying this, people trying that. At the end of a year or two there was only one drug left standing, AZT. A lot of magical thinking goes on.

Tegan Taylor: Well, that's enough of my questions. Coronacast is all about answering your questions, the audience questions. So one really common question we are getting, Norman, is about work clothes, how we can safely manage our work clothes when we get home.

Norman Swan: Particularly if you are in a job where you are meeting other people, say deliveries and that sort of thing, and there's just no option but to contact other people, it is possible at the end of a day that you've got some coronavirus on your clothes, in which case you probably should take off your outer clothes outside and take them in and get them washed, and washing in detergent will get rid of any coronavirus that's on them. If you don't have that option, then really all you can do is take off your clothes outside so nobody else comes in contact with them and just leave them there. If you've got a second set, then wear the second set, and the first set after about a day any coronavirus on it should have disappeared.

Tegan Taylor: We've got a really good question from Niamh who is aged six, asking; when we are washing our hands we are washing away the bad germs, but are we washing away good germs too?

Norman Swan: Yes, you are, that's just one of the things you're going to have to accept. So Niamh has obviously heard of the microbiome which is on the inside as well as the outside of your body, and yes, sure, by washing your hands with soap and water you will get rid of some of the good germs, but the bad germs prevail. Those good germs can come back. On your hands themselves, it's not as if they are doing you an awful lot of good, you're much better to get rid of the bad germs.

Tegan Taylor: What about temperature checks? So we've got someone asking whether large-scale temperature checking is useful. We see that happening a lot overseas but Australia is not really doing this.

Norman Swan: The evidence isn't in. There are certain features of countries that seem to be controlling this well, and it is about temperature checks, temperature checks at the border, not that that's relevant anymore, going in and out of buildings. And if you've got a fever then you get tested. There is no doubt that that sort of thing will pick up more people who are symptomatic, it will pick up people who have got the flu or other respiratory viruses as well as COVID-19. And in an environment where you want to pick up as much COVID-19 as you possibly can, isolate it in quarantine, find their contacts and quarantine, it's one tool. It's not a proven tool, but it's one tool. And we don't really know, but what the World Health Organisation would argue is don't let the perfect be the enemy of the good, do it and worry about whether or not there is evidence base there. Are you going to do any harm? Very unlikely.

Tegan Taylor: Another question from our audience; can two people who both have been diagnosed with COVID-19 live together in the same house? They don't need to isolate from each other, do they, they're not going to make each other worse, are they?

Norman Swan: It's a very good question which I don't know the answer to. But the answer is that in China they had these vast quarantine hospitals, and they've got them elsewhere as well in an open environment, where COVID-19 people are there in very large numbers. I don't know whether they studied…it's not a controlled environment so you wouldn't know. In theory the initial viral dose can determine whether or not you get a severe infection, but whether you can get a super dose on top I think is uncertain. So I think that on the balance of things, if two people are COVID-19 positive, it's going on the basis that quarantining brings those sorts of people together anyway, there is low risk of harm I imagine.

Tegan Taylor: One more question from the audience. There is someone who is noting that in Italy and Europe the virus has killed younger people and adults who don't have any previous medical concerns. Is it possible that the virus in Italy or Europe is more aggressive or more contagious than what we are seeing in Australia?

Norman Swan: It doesn't look that way. I've covered this a lot on the Health Report on Radio National. The virus does not seem to be mutating into an aggressive form or a less aggressive form at this stage, it's simply a matter of numbers. There is such vast numbers of people infected in New York, in Italy and in Spain and to some extent France, that you're just getting what is a relatively rare event, unusual event happening commonly simply because there's so many infections. If there's thousands of people getting it, you've got hundreds and hundreds of people who are 30 and 40 coming through with the illness. So it's not because it's more aggressive, it's just that the pandemic has been allowed to slip to get to very large numbers and they just flow through to intensive care and deaths.

Tegan Taylor: So, as usual, let's talk about a bit of research today. We are hearing every day that physical distancing is critical, but there is a new preprint paper out these past few days that is actually quantifying this. The paper is from the London School of Hygiene and Tropical Medicine which is well known for mathematical modelling. Norman, what does the paper find?

Norman Swan: They did a survey of adults after lockdown in the UK to ask about who they came into contact with, what their ages were, whereabouts, how well people were sticking to the lockdown measures. And what they found is that, assuming that people were telling the truth, compared to pre-lockdown, there was a 73% reduction in contacts with other people. So an average of 10 contacts a day down to 2.9. And what they then did was they modelled that sort of reduction, if it was nationwide, what it did to the R0 value. The R0 value is how many people a virus infects at the beginning of the epidemic. So, in other words, when there is no control and it's just let loose on the community, how many does it infect. And COVID-19 virus, SARS-CoV-2, it's between 2 and 3, it's probably a bit nearer 3 than 2, is the number of people infected.

Anyway, the bottom line for the mathematical modelling from this study was if that applied to the British public as a whole, the R0 went from 2.6 to 0.62. In other words, it went below the magic line of 1, so that meant each person was infecting less than one other person or fewer than one other person, and that means that you are actually flattening the curve because the rate of spread has gone below 1. So each person doesn't represent another person, it's even less than that, so that's when you start to get to the epidemic tailing off.

Tegan Taylor: Well, that's it for Coronacast today. If you want to send in a question, go to abc.net.au/coronavirus, and a reminder that we now have transcripts of each episode on the Coronacast website, and, if you like this podcast, please tell a friend.

Norman Swan: And we'll see you tomorrow.

Tegan Taylor: See you then.