As Melbourne relaxes restrictions, can it keep cases down?

Will Ockenden: Hello, this is Coronacast.
Norman Swan: I'm physician and journalist Dr Norman Swan. It's Monday, 28 September.
Will Ockenden: And I'm Will Ockenden, Coronacast's producer, I'm filling in for Tegan Taylor this week who, after 147 episodes straight, is off taking a little holiday. She'll be back next week.
Norman Swan: They're soft these days, gosh, she needs a holiday after only 147 episodes! But we welcome you, Will.
Will Ockenden: Thank you very much. So Norman, you might have noticed yesterday a big press conference from the Victorian Premier Daniel Andrews announcing a few changes to the state's reopening and step back to Covid-normal. We haven't spoken a lot about Victoria lately, but it really does seem like there is a very positive story in Victoria now. It seems like they are ahead of schedule when it comes to the number of cases and where they thought they'd be.
Norman Swan: Yeah, no, no, it's really great news, and even I think some of the testing has gone up a little bit as well, which is really good too. 16 cases, still a lot in aged care, but one unknown and that's really good news where you're just starting to know where all the virus is in Victoria and narrowing that down. So it's great news and a little bit of the foot off the pedal a little bit in terms of the brake pedal which will make an enormous difference to people in stage 4, just to be able to get out a little bit more, some of the kids getting back to school, you've got some definite dates there, and it's great news.
Will Ockenden: What's interesting about the number of new cases yesterday, there was 16 announced and obviously we don't know what's going to be announced quite yet today, but as you mentioned, 15 of those they've linked to other cases, they seemingly split them differently than other states, they've got ten in aged care and they've got four is what they call complex cases, and I'm not really sure what a complex case is. Do you have any idea about how the Victorian departments are categorising things?
Norman Swan: I assume that it's where they think they know where it is but it could be one of two or three sources but I really don't know. Victoria is a bit notorious for inventing new categories, but having said the word 'notorious', the whole of the community is doing really well.
Will Ockenden: Obviously as they release restrictions it does increase the risk of transmission and outbreaks but obviously you've got to do it because you can't stay in lockdown for the rest of your life. Do you think that as Melbourne relaxes restrictions it can keep the number of cases down?
Norman Swan: I think they are doing it in the right sort of stepwise way, what's called second steps that is being announced that cover a whole series of different areas. The effective reproduction number is well under 1, according to the analyses that have been done. But on the flipside, an analysis has been done by the Burnet Institute, this does not necessarily predict the future but it really tells you where things might go, and what they've hypothesised is if you took your foot completely off the brake pedal and just let things rip now, go back to normal, there's a 41% chance that within two weeks you'd have an average of 100 cases a day. So we are not ready yet, and that is based on presumably the amount of circulating virus they think there still is in the community which would just explode if people started mixing again. The reason it's under control is that we still have very significant social distancing.
Will Ockenden: So the Victorian government, do you think, is still taking a very cautious approach, despite obviously 127,000 people now going back to work as of Monday and other restrictions being lifted slowly from there?
Norman Swan: It's a risk-based decision and there are risks in lifting the restrictions now. But as you said earlier, Will, you've got to do it at some point, and hopefully this is a measured lifting which mitigates risk as much as possible.
Will Ockenden: Okay, let's go to some questions, and I think we'll start with sewage, a favourite topic of yours…
Norman Swan: Yes, absolutely.
Will Ockenden: We've had questions from Wendy and Laura asking about how useful sewage testing for monitoring community spread of SARS-CoV-2 actually is.
Norman Swan: So sewage is not necessarily useful for measuring community spread of SARS-CoV-2, it's more how much SARS-CoV-2 might be out there that you are not picking up through your testing regime. If you like, it's a backup to see whether or not you are testing enough and whether the virus is circulating. And it's fragments of the virus, it's not necessarily the live virus that you're finding.
It's a bit fraught, it's not necessarily hugely accurate, and you've got to control really well for it. You might remember, Will, that there was an announcement that SARS-CoV-2 had been found in the sewage in Barcelona last March, so that's March 2019, but in fact that's really controversial, it probably wasn't controlled properly, so you've got to be really careful how you do this. But it does give you an indication of whether or not there is virus out there, not necessarily spreading, it could be just somebody who's got it. The gastrointestinal tract is actually quite a good place to find SARS-CoV-2. A high percentage of people who have got it, they've got it in their bowels as well.
Will Ockenden: Do we know how long it lasts in the sewerage system? Because over the weekend New South Wales Health put out a press release talking about how it's done. It has been obviously doing some quite wide-scale testing across many areas of Sydney, like Bondi to Cronulla, Penrith et cetera, and that actually found positive samples in three of those areas in which they tested. Do we know how long it actually lasts in the system? Is it giving you what happened the night before or could it have been there for many, many weeks?
Norman Swan: That's a very good question and I don't know the answer to it, but remember it's not live virus, it's just viral fragments. I actually don't know the transit time and I assume for different sewerage systems the story is different, that some sewerage systems may have a slower transit time because they go longer distances. I don't know the answer to that, it's a good question though, and maybe I'll take it on notice and we'll try and answer it in a future Coronacast.
Will Ockenden: So on weather, this comes up quite a lot in the questions that we get because people have correlated various waves and second waves and said it seems more likely that they happen in winter. Tom has written in and says as Europe's second wave takes off as their northern winter approaches, he's surprised that there has not been more attention on the role of climate in community transmission. Has there been any update on this as we, again, switch seasons, the northern hemisphere going into winter and Australia coming out of it and going back into summer?
Norman Swan: So it's important to notice that the second wave in Europe has occurred in September during warm temperatures. So it's not cold in Europe yet, people haven't yet retreated inside. So it's late summer, early autumn that you are getting this surge in the second wave, while it's still quite warm. In many of the states where it's coming back in the United States, it's still warm there too, in fact you've got bushfires.
So whilst winter theoretically increases the risk of transmission maybe by about 20%, you can't blame that on the second wave in Victoria. It may be a factor in sustaining the second wave if it goes into October and November, but not at the start of it. I think this pandemic is so widespread in a non-immune population that it overwhelms the effect of climate. And I haven't seen much new information on that. Largely they've got to see the pattern that emerges over the first year or two of the pandemic to really be sure.
Will Ockenden: In the question from Roger about sniffer dogs. He says there has been quite a bit of press about dogs being able to sniff out COVID-19. I haven't seen many articles on this, I'm not sure if there has been any scientific articles. Have you heard anything about training sniffer dogs for COVID-19 testing?
Norman Swan: This has been an area of research now for some years. It started off with ward sisters being able to tell you if someone is going to die the next day, they could just smell it. Some people say that they can detect when somebody has got cancer because they can just smell it on them.
They've tried to train animals to make that sort of diagnosis or sniff out diagnoses like that, and they've also tried to analyse what chemicals are being detected so you could put into a device and do something like a breathalyser. Not hugely successful.
And I think here what we are dealing with is something that's holistic. If you train a dog, try to sniff out somebody who's got COVID-19 versus somebody who hasn't, can they do it reliably? Then you might try and do a chemical analysis, but it's much easier just to let the dog have a go.
Will Ockenden: So just some feedback before we go. Carolyn has written into say last week you mentioned that you didn't want to jinx the delivery date of a vaccine by saying it could come out as early as January. 'Does Norman believe in the power of the jinx?' She does but it's been an ongoing argument with her husband, so 'if Dr Swan can back me up on this, I would appreciate it.'
Norman Swan: It's just a reflex thing like touching wood, jinxing, feeling it go wrong, superstition. I don't really believe it, but it's a reflex action thinking, well, just don't push your luck. As much as I'd like to back you up Carolyn, I don't really believe it, it's just an automatic reflex.
Will Ockenden: And Kenton has just said…because we talk a little bit about testing times, and in the ACT Kenton got a test at 6pm and got the negative result via SMS at 3am, less than nine hours later, didn't even miss a day of work for isolation. So there's a little example for you on speedy test results from the ACT.
Norman Swan: That's right, he just didn't get a good night's sleep because he got woken up at 3am by the ping.
Will Ockenden: Well, that's all for Coronacast today.
Norman Swan: We love your questions, and if you want to send one in, go to our website, abc.net.au/coronacast, and click 'Ask a Question'. Mention Coronacast so we can find it.
Will Ockenden: Leave us a review on Apple Podcasts if you can, and we'll be back tomorrow.
Norman Swan: See you then.