Featured researcher: Professor Catherine Bennett

• 27 November 2020: "Twenty-eight days without new cases for Victoria, and hopefully NSW will announce today that they have reached 20. Adelaide looks like they have this cluster under control (contacts of contacts pays off yet again) with only one new case reported. Victoria has reported some positive sewerage tests and so we do need to keep our testing rates up, and we need to practice those precautions that mean even if the virus is out there, it won’t have the opportunity to take off quickly. We have this Australia, but we all have to keep actively working on it individually and collectively to hold on to this... the positive wastewater results in our south west are a reminder."

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Restrictions and lockdowns

• 19/11/2020: Experts, including Deakin University Chair in Epidemiology Professor Catherine Bennett say SA got it right, even if the measures seem overly restrictive.
• 18/11/2020: Epidemiologists say six-day lockdown enough to contain SA outbreak
• 14/11/2020: How an Australian state beat its second wave of COVID-19
• 10/11/2020: Watch as Catherine talks about how Melbourne got on top of the second wave Melbourne Crushes Covid-19
• 9/11/2020: Victoria's achievement in bringing down daily coronavirus numbers from 700 new cases a day in August to none in the past 10 days has led Ireland and other European countries to seek our experts' advice on how the state did it. Zeroing in on Victoria's suppression success
• 8/11/2020: “We were more sedate after wave 1 in Melbourne (according to mobility measures and number of close contacts) and will be interesting to see what happens this time. Feels really busy in places already, but to be honest we have all adapted so much to isolation so hard to judge!” After Crushing Covid, Melbourne Emerges Wary and More Sedate
• 6/11/2020: “Victorians may be rewarded on Sunday after their perfect week of zero coronavirus cases with a more widespread easing of restrictions than had been planned.” After seven doughnut days, Victoria set to be 'much closer to normal'
• 1/11/2020: Catherine Bennett: Now that Melbourne’s COVID-19 lockdown has ended, what’s next?
• 31/10/2020: “Victoria may still have some work to do in communications and case management, but in all other respects we are there with contact tracing. And with our numbers down (only 1 new case today, 14-day average at 2.4 and 2 mystery cases in a fortnight), we should now be able to keep numbers down and outbreaks contained so that we never have to test the system at high case numbers again! NSW continues to have low-level community transmission with 20 cases in the last fortnight, averaging 1.4 cases a day. I am not sure why so much emphasis is being placed on “difference” when arguably we are in the same boat, although Vic has the advantage of less risk of wider community transmission for now at least as we emerge from our extended lockdown. Let’s hope both states can close off community transmission.. then we can celebrate together, move fully to prevention mode, and borders won’t be an issue!” Top epidemiologist rates Victoria’s contact tracing as the ‘gold standard’
• 28/10/2020: Victoria and only a handful of countries have achieved zero from second wave

• Melbourne's reopening is on a 'cautious pause' as authorities await the results of thousands of tests from the city's north: Why Melbourne's coronavirus reopening is on hold as regional Victoria steps forward

• “We should be able to manage this regardless of whether we are open or not. Part of this spread could in fact be due to the challenge of getting complex information to families in a way that allows them to do the right thing. We need a clear explanation about why the system can't cope and why we aren’t opening.” Premier's 'cautious pause' draws fire after plans thrown into disarray by outbreak
• "I really hope we get through October and see the end of the ring of steel before November or by November." Victoria could remove ring of steel border around Melbourne next month, Daniel Andrews says
• Coronavirus Victoria: Melbourne makes world history crushing second wave
• City's 5km limit could go to 20km, with models being run 'as we speak'
• Epidemiologist weighs in on whether Melbourne’s COVID-19 rules should be eased
• Victorian 'pivot' opens path out of lockdown
• A 14-day rolling average of 5 new daily cases is the wrong trigger for easing Melbourne lockdown. Let’s look at ‘under investigation’ cases instead
• Catherine talks to 10's The Project: The Project TV: Time To End Lockdown?
• Catherine talks to ABC NewsRadio's Thomas Oriti about how being able to control outbreaks is the key to lifting restrictions Tougher Covid-19 restrictions in Victoria
• “Case numbers don’t necessarily mean Melbourne has to postpone moving to step three, which would involve allowing outdoor dining for cafes and restaurants from next week” Which COVID restrictions are likely to be eased next week?
• “Another 14 cases today, but who’d have thought we’d be disappointed with a 14-day average under 10! Burnet modeling commissioned by DHHS had us with only a 17% chance of a resurgence if we opened up to the final step with up to 10 new cases daily, and even that assumed no ramping up of our outbreak response as numbers started to climb.. and predates the contacts of contacts “ring of containment” now being deployed. We are therefore more than ready to go to just the next step! We need to hear more of these positive predictions.” The new Covid-normal: is Victoria ready to come out of lockdown?
• "With case numbers in the community dropping in metro, including at least 3 days in a row this week with zero mystery cases, there is more chat about the next steps for both metro and regional Vic. The focus for most of us now is on suppression of risk, not suppression of actual transmission. That is, the suppression of seeding potential and of outbreak potential. If the virus happens to land in a worker who takes it home to another part of town or the State, then the less mixing there this, the more likely it is that it will simply die out, or be contained effectively if known about and tracing done.
  
  If the regions move another step, then the State remains out of sync. The Premier has already suggested the State may not reunite even if metro does move to join regional Vic on Step 3 on ~ Oct 19. Hopefully this will all be moot if these outbreaks are shut down in the next 2 weeks. Then we can be back in sync and move as a State towards the last steps. Melburnians staying the course under very strict lockdown for the sake of these small outbreaks is probably as frustrating as it is for regional Victoria under restrictions with no cases. It will be a great day when we can move to the final step and put this difficult phase behind us." Low COVID-19 case numbers have regional businesses straining against Victoria's restrictions
• Our COVID-summer will look very different
• Daniel Andrews will detail the next step in Melbourne's coronavirus restrictions roadmap today
• "If people are taking care and we're moving to step three … [the outbreak] is contained, it's not high-risk" More COVID-19 restrictions may be eased in Victoria on Sunday. Here's what the health experts think
• "It's unlikely there is now underlying community transmission in regional Victoria because of the length of the lockdown" Safe for NSW to open up to regional Victoria, experts say
• "Victoria's dropping case numbers are "tracking better" than modelling initially suggested and the state's daily figures could warrant fast-tracking the lifting of lockdown restrictions." 'No epidemiological argument for border closure' if case numbers fall at this rate
• If you take out the positive cases linked to known outbreaks, the proportion of cases coming back positive dropped to below 0.1 per cent. Victoria should take 'cautious' approach to early easing of coronavirus restrictions, expert says
• The lowest 24-hour increase since nine cases were recorded on June 16 brings Melbourne’s rolling 14-day average to 34.4. 11 new cases, two deaths; Melbourne’s harsh lockdown could end weeks early
• Common sense must guide us on this road map, and will allow a shift in focus to the important business of evidence-based prevention, early warning systems and testing strategies, backed up by contact tracing and outbreak response readiness, writes Catherine Bennett in The Age Dropping cases should lead to a 'common-sense' rethink on opening up
• Catherine Bennett chats to Patricia Karvelas on RN Drive Victoria to boost coronavirus contact tracing
• On 6 September, the State Government announced the stage four lockdown would be extended by two weeks, with more significant restrictions to be eased in late October. Experts question model and map as new cases fall to lowest since June
• The Victorian Government's roadmap to easing coronavirus restrictions has been met with varied reactions. Victoria's coronavirus restrictions roadmap could exacerbate anxiety and prolong economic pain, experts say
• Catherine's thoughts on Victoria's roadmap out of restrictions Steps out will be incremental, frustrating, even arbitrary
• The Conversation asked four experts, including Catherine Bennett, what they see as the most important aspects of Victoria’s path out of stage four. Four perspectives on how Victoria should exit stage 4 lockdown
• Allowing households to open their doors to one or two close friends and family in a 'germ bubble' is being considered as a possible route out of stage four lockdown and the loneliness that goes with it. The lonely and the learned back 'germ bubbles' as the way to ease lockdown
• COVID curfew crunch: Nearly $1 million in fines but medicos are split on its effectiveness
• “Evaluation of interventions now will allow us to move from blunt shutdowns to precision tactics in our COVID-19 fight, and help chart our way out of our current lockdown safely.” Stage four lockdown offers a chance to find out path out
• “The Stage 5 threat - not the best way to encourage compliance. The compliance engineered into stage 4 should be more than enough to bring this under control. Otherwise, we risk going to even more restrictions to stop people from mixing, or give up on control attempts and live with consequences. Doesn’t bear to think about either, so let’s make this work and work fast!” Stage 5 ahead? What Melbourne could face if COVID cases don’t decline
• “Lockdown is the key to killing off clusters that we can’t see, as well as the ones we can. Arguments for a “stage 4” lockdown are lost on me... why use a NZ style shutdown when consensus is that was overkill first time round, (especially as Aus and Melb achieved same outcome) and there is no evidence it will make a difference given current epidemic dynamics. Reduced mobility, more distancing, masks and isolation if symptomatic is the path to shutting this down.” Victorian lockdown high COVID case numbers mean longer lockdown necessary

Masks and face coverings

• 9/11/2020: Catherine chats to 3AW How epidemiologists think Victoria’s mask rules should change
• 9/11/2020: Major change to Victoria's coronavirus rules: Masks may no longer be compulsory in public as the state heads towards a week of no new cases - but there is a catch
• 8/11/2020: “Premier Daniel Andrews has ended Victoria’s state of disaster, disbanded the crisis committee of cabinet and after 124 days opened the “ring of steel” which had kept Melburnians out of the regions as a reward for a ninth day in a row of no new coronavirus cases and no deaths.” Masks should go, experts say, as 'ring of steel' is abolished
• 5/11/2020: “Victorians are still getting used to wearing masks every time they leave the house but not everyone's wearing them correctly — and health experts say the messaging needs to be much clearer.” Victoria coronavirus rules on face masks should be clearer, experts say
• 1/11/2020: "We know that [masks] reduce risk dramatically — in some settings they say masks can reduce the risk of people becoming infected by up to 50 per cent." Low COVID-19 risk in regional Victoria, but this is no time to take off your mask, expert says
• Victorians must now wear fitted face masks instead of bandannas, scarves, plastic face shields as masks have been deemed more effective at stopping droplet spread. Masks are better than face shields: Experts say why
• Watch as Catherine talks to Skynews about Victorian restrictions.Stage three and masks are 'surely enough to manage COVID-19' in Victoria
• Research suggests the growing use of alternative face coverings may not be helpful in curbing the spread of COVID-19. Face shields not effective replacements for cloth masks, experts say
• “Warning - this story refers to facts and therefore may be considered offensive by some. Congratulations to SBS for pulling together this response.” Fact-checking Andrew Bolt’s claims about Melbourne’s mandatory mask order

Testing

• 22/10/11: NT adopts 10-minute COVID-19 tests, but other states remain wary of false negatives
• 10/11/2020: Victoria is preparing to launch its first large-scale asymptomatic testing program as the state's run of no coronavirus deaths or cases continues. Large-scale asymptomatic testing program launched in Victoria
• 4/11/2020: “With low case numbers and coronavirus fatigue setting in, is it time to make testing more palatable and favour quantity as much as quality?” COVID trade-offs: How to keep testing rates high
• Weekly testing looms for one in four workers in abattoirs, supermarkets
• "Unless the pattern changes in what they're seeing when they go out to contact tracing, or unless the proportion of the positives starts to go up, then I think this is a good enough indication that our testing numbers are following the proportion of people with symptoms." Victoria's coronavirus case numbers are declining, but are testing numbers sufficient to be confident about the numbers?
• "Testing remains critical, even when our test positive rates are 0.1% or 1 in a thousand. This is especially true whilst a few cases still appear where a source cannot be found. If one person infects two others who are not linked, and that first person does not get tested but the other two do, then we not only miss one case, but we “create” two mystery cases - and these will be more critical in decisions about easing restrictions than +/- one linked case." NSW coronavirus testing rates are plummeting — here's why that's a problem
• AusSMC BRIEFING: Genomic testing for COVID-19 - ask the experts
• “High rates of positive test results will happen as clusters with high transmission risk are investigated. The positivity rates track closely with the number of linked cases among new reports. This clouds our view of the actual background positive rate in the wider community.” Should I get tested? What if I don't have symptoms? Will it hurt? Your COVID-19 testing questions answered

Community transmission and contact tracing

• 26/11/20: "The Adelaide story continues to be unpacked. The first case was not the cleaner it seems, but a security guard. This not only means that it is now not proof that the initial infection was from contaminated surfaces (the cleaner had no contact with returned travellers), it also is another piece removed from the 'this strain is different' scenario that led to the context that made the infection of a man who only collected a pizza cooked by a case in the kitchen seem plausible.
• These bookend infection stories ,with some short incubation period chains of transmission in-between, conspired to create the case to close down a state.
• You can only base your decisions on what you know.. a pity two stories presented in quick succession in a way that made them seem more aberrant than they actually were, therefore making SA Health less suspicious than they otherwise might have been. This is real life epi.
• The cleaner must have had a short incubation period to have looked as if infected before the security guards. The other case’s in this person’s family also becoming infectious quickly.. with mild symptoms .. which might fit with a family with an immunological propensity for this epidemiological picture. Not a bee strain as was feared."
• 21/11/20: Catherine talks to ABC News Radio about SA’s outbreak ABC News radio
• 19/11/2020: “Contracting coronavirus via a surface is considered somewhat rare, but it's exactly what seems to have sparked a cluster in Adelaide's northern suburbs.” How did coronavirus spread from a hotel surface to Adelaide's northern suburbs?
• 17/11/20: "The latest news out of Adelaide is that surface contamination may be to blame. Now two security guards as well as the original cleaner infected at the medi-hotel, plus family members and close contacts of the cleaner and one guard now bring the number to 20 with one more just announced but not yet linked.
  
  Given the risk at these hotels and the costs when the virus escapes, why aren’t we paying staff more so they don’t have to work across multiple locations? We also should be doing saliva testing daily. None of this protects the border 100%, but it would help lower the risks further. If next cases notifications are those close contacts in isolation who have returned a positive test initially but are being tested again, then this increases the chances they spent their entire infectious period in isolation. That would be good news.
  
  This virus arrived in Adelaide with a returned traveler on November 2. We will be lucky if it’s just two generations of spread .. but shows how quickly 1 becomes 21. Still, this is not Melbourne in June. There are already 1000 people in isolation in Adelaide. Victoria did not follow up this aggressively, we had many families infected simultaneously, and many workplaces involved. Complicated nonetheless." How did Adelaide's COVID-19 cluster begin and are medi-hotel procedures to blame?
• 7/11/2020: “In early September, as Victoria's daily COVID-19 case numbers were finally dropping out of triple figures, Premier Daniel Andrews announced the creation of a system of local response units in Melbourne, to replace the highly centralised system that had failed to stop the second wave.” Melbourne's suburban coronavirus contact tracing teams were supposed to be running by now. So what's the hold-up?
• 7/11/2020: “Victoria has continued its streak of zero COVID-19 cases, with no new infections or deaths reported on Saturday, but a positive swab showed a case linked to aged care is still shedding the virus.” Victoria records zero new cases, but viral shedding found in a case linked to aged care
• 5/11/2020: “Amid fears that a coronavirus outbreak would spread quickly among campers, the Mornington Peninsula Shire will keep three of its council-managed camping grounds closed until February…” No Christmas under canvas after council slaps a COVID ban on camping
• 31/10/2020: Victoria has ramped up its highly criticised contact tracing system to a “gold standard”, according to a leading epidemiologist Top epidemiologist rates Victoria’s contact tracing as the ‘gold standard’
• 29/10/2020: Now we're opening up, testing and contact tracing really matters
• 26/10/2020: Restrictions ease, but ‘main problem’ with Vic contact tracing remains
• "We've got a much more front foot local team who can get to the site of a case or a cluster very quickly. That's going to make the difference between having a case, and having a wave." As coronavirus cases plummet, it's time to ask: Is Australia ready for the third wave?
• Blowout in city travel times predicted as lockdown eases
• Which countries are doing well with contact tracing for coronavirus? A look at South Korea, Singapore, China, New Zealand and Belgium
• Sydney versus Melbourne: what the experts say about the COVID numbers comparison
• Where have Melbourne's recent 'mystery' COVID-19 cases been found?
• “The index case truck driver who took the virus to Kilmore and Shepparton would have already been isolated and prevented from making that journey if the ‘contacts of contacts’ approach had been introduced a week earlier (dCHO confirmed today). Our numbers have been low enough to invoke this for some weeks now, and of course I have been advocating for it for many more weeks than that. I do not think NSW does do this routinely btw, I only heard brief mention of it once when they discovered 3 chains of transmission had occurred within 10 days. So it is great that Victoria is now taking this active step to help suppress these clusters early. Better late than never, but a pity we were just a few days shy of preventing this double cluster.” Contact tracing delay and a failure to reveal all threatens to spark Covid outbreak in regional Victoria
• "Victoria’s contact tracing system has faced criticism in the past for being inefficient, with officials flying to NSW in September to learn from that state. Comparisons are difficult in a pandemic because each outbreak has its own unique characteristics. That said, there are some key features that underpin the differing responses of NSW and Victoria when it comes to contact tracing": Where did Victoria go so wrong with contact tracing and have they fixed it?
• Coronavirus Australia:‘Won’t be able to control the spread’: Urgent warning for NSW
• 'The sentinel surveillance is a key step to not only protect facilities from staff attending work whilst infectious, even if they are unsymptomatic.' How Victoria can cement its gains, put a lid on COVID hotspots and start getting back to normal
• Catherine Bennett on the ABC’s 7.30 Report Victoria has overhauled its swamped contact tracing system
• The Victorian government is implementing changes to its contact tracing system including moving to a suburban hub model similar to New South Wales. A day in the life of Victoria’s Covid contact tracers: ‘The puzzle is blank and once you get it together it's fantastic'
• COVID quarantine hotel sex: The rumour that triggered Victoria’s tidal wave of consequences
• “Finally! recognition for hardest hit low SES suburbs. I have been telling this story for a while now, but it has been left on the editors chopping block.” Expert on who REALLY should 'be credited for turning Victoria's COVID tide'
• “We have known SARS-CoV2 moves in clusters through communities since early on. Comparing Victoria and NSW is a great demonstration of the different outcomes if a new wave of infection is only discovered once multiple clusters have established simultaneously. These events feed more virus back into community that then seed more clusters.” Super-spreaders could be key to controlling COVID-19
• “Epidemic curves by LGA grouped in SES quintiles is even more interesting than could be covered in this story. Despite the outbreak being seeded in these communities and large clusters already well formed by the time any restrictions came in, and the fact that people in these areas are less able to work from home or be able to afford to stop working, the rate of drop is proportionally as great in these communities once the excess numbers from local outbreaks start to be contained. These low SES areas not only had the extra serve of bad luck at the start, they have collectively done an amazing job at being part of the public health solution.” 'Past the peak': Cautious optimism as state posts fewer new COVID-19 cases
• “Those unlinked COVID-19 community cases … if we can break these unseen chains of transmission.. we will have this beat!” Disease detectives baffled by mystery COVID-19 cases behind tough new lockdown
• “More detailed modelling of mobility and distancing data finds that Victoria was best in Australia when the reintroduction of COVID-19 occurred, and the suburbs at the heart of this were no different to others in Melbourne. This report also confirms that COVID transmission via clusters defies normal measures of epidemic potential. This comes back to my previous comments on the element of chance in where the virus lands in the community.. and the impact that this can have.” Victoria’s social distancing best on mainland when second surge hit

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• 20/11/20: A leading epidemiologist has argued workers in hotel quarantine need to be paid more so that they don't work other jobs and risk coronavirus infection. Could higher-paid hotel quarantine workers better protect Australia from COVID-19?
• 18/11/2020:  “South Australian six-day circuit breaker lockdown: let’s hope it’s enough to ensure they have found the edge of this cluster. The next few days will tell. Five generations of spread in less than two weeks makes it a challenging fight.
  They were not aware of the leak till an elderly second generation case attended an emergency department and the doctor decided to run a COVID test even though the respiratory symptoms were mild. This could have made all the difference.
  Testing the staff at med-hotels would have been better again, picking this up a generation earlier .and there might not be 4000 in isolation or an entire state locked down for six days.
  Let’s hope this works for South Australia’s sake, and because it matters a lot to the rest of Australia. It will also tell us if this short burst of extreme lockdown is a useful strategy to consider when dealing with a point source cluster that is not discovered until there have been a few generations of spread.” South Australia's 6-day lockdown shows we need to take hotel quarantine more seriously
• 12/11/2020: “Is Victoria a model covid-19 response? Our story is one very different from what is happening in Europe now. We had the first wave contained through early introduction of six weeks of stage 3 lockdown, but we missed the start of the second wave when the virus was reintroduced from hotel quarantine breaches. We then had a large and long second wave largely driven by healthcare outbreaks, especially aged care, whilst Victoria was held in lockdown until these were eventually closed off ... and we had a public health response that could cope with opening up. Add to that a government so concerned about a third wave that it was believed we had get numbers extremely low “to keep them low”. That all ends up looking like 4 months of lockdown... and at what cost? The Victorian response must be judged on the extent and duration of lockdown, and the reasons behind the need for such a long lockdown, .. just the case number outcome.” What is behind Victoria's suppression success, and will it last?
• 7/11/2020: “Coronavirus could "die out" in Australia entirely if New South Wales and Victoria stay on their current trajectory of low infections, according to two leading epidemiologists.” Coronavirus could disappear in Australia if NSW and Victoria maintain control over next few weeks, experts say
• 3/11/2020: “Europe is beginning what Melbourne has only just finished: a second lockdown.” Podcast: Has Europe left it too late?
• 25/10/2020: As coronavirus cases plummet, it's time to ask: Is Australia ready for the third wave?
• "An opinion piece with colleagues .. we did not come up with the title and of course the comments relate to the title rather than the piece.. but I hope you appreciate the read!" COVID success will only come when Premier trusts the public
• “Throwing some numbers around... if we have to count anything, then we may as well count in a way that captures where the real risk is (unlinked cases) and the linked cases where there is still some work to do… especially if these are casual contacts who may not yet be in quarantine.” A 14-day rolling average of 5 new daily cases is the wrong trigger for easing Melbourne lockdown. Let’s look at ‘under investigation’ cases instead
• Doctors stoush over Victoria's extended lockdown
• With cases stubbornly staying in the double digits, is there any light at the end of the tunnel? What was that about being OK for Xmas? Lockdown life in Melbourne shows no let up
• “The CHO said today that once a close contact develops symptoms, DHHS will now consider them to be presumptive cases before they receive their tests results, and follow up their contacts immediately. So contacts of contacts will then be notified and asked to isolate as a precaution in case they are infected and heading into their pre-symptomatic infectious period. That’s exactly what’s needed when we have rapid spread with nearly 30 cases in 10 days in first and second level contacts. It sounds like DHHS might do this more extensively in outbreaks now - The real advantage of having lower numbers. The complexity of this outbreak shows what was happening many times over when there wasn’t the clarity or resources to see and investigate outbreaks with cases embedded in amongst 100s of new cases a day. We are in a whole new world now.. still extremely hard work for the department, but much more possible for the health teams to contain these outbreaks.” Victoria enters uncharted waters, urged to trace contacts of contacts
• "Time to gather the information needed to fuel the difficult but necessary debates about how we live with the virus - we had limited choices when COVID-19 was such an unknown, but all action, and inaction, comes at a cost (lives, health, economic and the myriad of societal impacts), and now we must comprehensively evaluate our strategies." Lockdown is working, but is it excessive?
• "We know hotel quarantine is not the perfect option, and not just in Vic. WA is a test case for us to determine how safe home isolation is for returned travellers, especially coming from low risk countries. If home isolation was successfully for many of our 20,000 known positive cases in wave 2, and for the quarantine of their close contacts who had a much higher risk of being positive than travellers returning from low risk countries, then this is an option to consider. Let’s hope evaluation of compliance in WA shows this to be a workable option, i’m sure Aussies wanting time come home (even from interstate) will be very relieved if this is deemed safe!" Coronavirus experts cautiously support Scott Morrison's plan for 'safe' international arrivals
• Health experts question 'incredibly conservative' road map
• “More modelling? The Burnet Institute team’s nuanced agent-based model calibrated to our second wave in Vic has more to offer. They found a 41% risk of another wave if we had jumped to the final roadmap step yesterday with our 14-day average at 22 (the previous conservative model said 62% for 14-day av. of 25).
  Many are now asking whether we still need the 5km rule. Or when will it be safe to move to step 3, and should the 14-day case count thresholds for this step be updated. These are the kind of scenarios that could be explored using this new model.
• The cases seeded into the model should reflect the different mix of case risk we have now (92% are linked and most therefore likely to be in isolation/quarantine when tested), but could be really helpful in guiding decisions on thresholds and timing of steps, as well as whether the 5km rule could be lifted. This is stopping some families from meeting outdoors or permitted businesses opening if clients aren’t local.
  It could also help people adapt to the roadmap changes (inc lifting of curfew etc), and help allay fears they may have about opening up. This will be very safe, our detection and response systems too, so we need to bring the people along with us who no longer believe that!” Melbourne's five-kilometre rule: is it really worth it?
• “Two months ago there was consensus among epidemiologists that to open up we would need new case numbers in low double digits and mystery cases to single digits. Since then it has all gone a bit crazy, but even after the road map was announced, there has been agreement that 5 cases was too ambitious and 10 cases a day is manageable. Over 70% if Vic’s cases are known to be linked when first reported, and therefore in people already in quarantine, and 85% of our cases under investigation are also linked eventually. We by now must have less than one mystery case a day on average (judging from changes in 14 day total). So why is a small number of contained but persistent outbreaks and 5 community cases a week not manageable? Sure we don’t want months of chasing cases like NSW has had to do, but continuing strict lockdown when we have already had 15 or more incubation cycles under it is clearly not the answer. We need to start easing restrictions, keep testing up, have fast and comprehensive case and contact follow-up, and remember the basics - distance, hygiene and masks. Then we can focus on prevention, early warning systems and monitoring to stay safe." What Australia needs to do to avoid a third Covid wave
• Chatting again about all things Covid-19 with Tass and Fiona on Joy radio’s Saturday Magazine Catherine Bennett, Epidemiologist
• “Divisive speak is dangerous - true always but particularly so in a pandemic. Opinions are being polarized; open-up completely or strict lock-down, you’re onboard or “you think it’s over because you want it to be over”, this virus is wildly infectious and cant be controlled without complete lockdown or you don’t believe it exists. Anyone with an opinion that doesn’t fit with either extreme is placed in to one to suit the commentator’s argument. These are worrying times. Most recently the narrative at the daily press conference is about regional and peninsula folk being terrified of Melburnians because of their “vastly higher amounts of virus”. Regional Vic’s 12-day av is a very low 1.9 cases/million, and the metro rate is also very low at 7.9 cases/million (half already in isolation). The Health Dept say they can finally see community transmission chains that were there all the time but hidden behind high numbers (data analyses could have shown sooner?). Stage 4 is about suppressing risk of transmission beyond these pockets where infection persists, creating the optimum backdrop for the Dept to do its work. 9 weeks in lock down has not been enough time for this (5-12 incubation periods), let’s hope another couple of weeks is.” - Catherine Bennett's LinkedIn
• RMIT ABC Fact Check: Were NSW's coronavirus numbers higher than Victoria's thresholds for lifting curfew, as Scott Morrison said?
• Has Australia really had 60,000 undiagnosed COVID-19 cases?
• Another week, and we will know more about our October in Melbourne. The Age has taken the lighter moments from today’s press conference to build hope. Also a useful discussion on whether those identified in breach of CHO rules in contact tracing interviews should be fined. Our enforcement strategies have placed us in a difficult situation - respect privacy, open up conversations in order to close outbreaks down, or issue fines. This is part of a bigger public health communication conversation about the way we engage community. Public health communication strategies needs to provide transparency, clarity and certainty, so that people come forward for testing quickly, then have the conversations to allow us to chase any transmission - without rapid testing and information handover, it is that much harder to contain outbreaks. Outbreak control always works better if enforcement is a last resort, and that is something we should try to find ways to avoid going ahead. Premier raises hopes of easing restrictions sooner than planned
• What is ‘herd immunity’ and what role does it play in a pandemic? Explainer: Reaching herd immunity in a viral pandemic
• “Think before you voice an opinion — consistent messaging is critical in a public health crisis. Expert debate can be valuable, but publicly opposing current interventions on the basis of opinion rather than fact can reduce efficacy by undermining public confidence, and therefore compliance... both of which are already harder to garner in a second wave.” Latest restrictions became a self-fulfilling prophecy

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(updated 30 September 2020)

The effective R number estimate and case count graphs: Reff can bounce a lot when case numbers are this low - if we have a low case count for a couple of days then it can appear to jump up after an incubation period (5-6 days) even if numbers are not that different. But remarkably we have only had two occasions when Reff peaked just above one, and the 10-day average is sitting around 0.6-0.7 and in fact has dropped this last week. This probably reflects that case and close contact follow-up is so much more effective when working with such manageable numbers, and working in partnership with the community. So easy for epidemic curve tails to be stubborn or unpredictable, so it’s great to see this steady downward trend continue right through to this end of the curve!

Notes:

• Many interventions were rolled in; we focus on the date where the main intervention became mandatory
• Not all cases are tested – only those with symptoms can be tested in the general community, and not all those will come forward
• When comparing the counts across the 5-6 day incubation period, we use raw new case numbers in the numerator, and the average of the case counts taken from 5 to 7 days previously in the denominator.
• The graph includes a 10-day moving average for the estimated R_eff to highlight the trends

What is R0 and how do we calculate our estimates?

The Reproduction number (R0 or “R naught”) has been talked about a lot during this COVID-19 pandemic. It is an important statistical term that reflects how infectious the virus is in different settings. Each time we change levels of restriction, or mandate masks, we are changing the number of close contacts people have and the risk that they will infect another person, and so R0 changes. We call the specific R0 in any setting R_eff; the effective Reproduction number.

R_eff summarises the average number of people who will be infected by each current positive case and tells us how our outbreak control measures are working. Those secondary infections will be counted as ‘new cases’ after they develop symptoms, seek testing, and when a positive test result is recorded. If the average number of secondary cases linked to particular cases is greater than 1, then R_eff is greater than 1. The number itself tells us how many people are infected by each case. So an R_eff of 3 indicates that each case infects another 3 new people on average, and that the outbreak is growing, with case numbers tripling every incubation period. For COVID-19, the median incubation period is 5 to 6 days.

On the other hand, if existing cases don’t all infect at least one other person, then the number drops below 1 and we know the outbreak is under control and case numbers are shrinking. If R_eff is, say 0.5, then that tells us that we can expect the number of new cases to drop to 50% of today’s new case numbers after one incubation period.

If we make certain assumptions, we can use the publicly available data to come up with a very rough estimate of the reproduction number for Victoria. If we assume that the time from infection to testing is reasonably consistent over time, then we can look at how new case numbers compare across incubation periods to estimate this R_eff. It is likely, however, that the time to testing for people with symptoms may have changed as the outbreak became more serious, and with hardship payments making it a bit easier for people to forgo work and get tested and isolate until they have their result.

Another assumption we’re making is that the proportion of true cases out there that are identified through testing remains reasonably constant as well. If you had only 50 % of cases being tested in one week, and then 100% in the next, it might look like R_eff had doubled, even if the true number of cases per day had not changed. This is true for all modelling where there is likely to be incomplete case capture, but as long as the proportion of cases that are counted stays relatively constant, then comparing even partial counts across incubation periods is still useful.

Case reports tend to come in batches from the outbreak investigations and the labs. For example, we see less reports on Mondays and Tuesdays as these are from tests completed on the weekend. Therefore, it’s useful to take an average of the number of existing cases on any one day. We use a 3-day average to smooth out those reporting fluctuations in the denominator of our calculation when we look at the ratio of new cases to those reported 5-6 days ago.

Finally, it’s important to note that the SARS-CoV-2 virus responsible for COVID-19 does not move through the population evenly. The number of people any one person infects is dependent on their number of close contacts and the environments they live and work in. It may also vary person to person based on their viral load, their symptoms, or other factors that may alter their potential to infect someone else. There have been many super-spreader events, whilst the majority of cases may not infect anyone else at all.

According to Victoria’s Chief Health Officer, Professor Brett Sutton, around one third of our new cases each day are from outbreaks, mostly in aged care and health facilities now. These have a big influence on our daily case numbers until these outbreaks are closed down and we stop seeing new clusters form.

All you need is a large super-spreader event, or a large new outbreak starting when someone takes the virus into their work place, and the reproduction number will change quickly. So, as always, this is not about numbers alone: the epidemic path is determined by where the virus is and who is exposed. Therefore, whilst useful to see how we are tracking, it remains very difficult to predict exactly where R_eff will be in another five days’ time.

Want to know more? What Is R0? Gauging Contagious Infections

(updated 5 October 2020)

Mystery case update (revised):

The 14-day weekly average case number and total mystery case number both continue to head down, though the curve is now slowing as the change becomes incremental. Even so, the average case number the week before last was 15, this week it’s 10, and the Reff remains around 0.7. The average will continue to drop steadily as those higher numbers drop off the other end of the 14-day window. Aged Care and Health Care related cases are dropping now, so when the Chadstone-related cluster is closed off we should have very few cases.

Brett Sutton said last week that maybe they might look at the number of cases that are still under investigation for the roadmap targets (those already linked in morning they are reported are likely to be in quarantine awaiting results). These includes some cases that will yet be linked to clusters, and the mystery cases. I too have been tracking this number for some time, and the good news is our 14-day average for all those under investigation on the first day of report is only 5. Yay!

The effective R number estimate and case count graphs: Reff can bounce a lot when case numbers are this low - if we have a low case count for a couple of days then it can appear to jump up after an incubation period (5-6 days) even if numbers are not that different. But remarkably we have only had two occasions when Reff peaked just above one, and the 10-day average is sitting around 0.6-0.7 and in fact has dropped this last week. This probably reflects that case and close contact follow-up is so much more effective when working with such manageable numbers, and working in partnership with the community. So easy for epidemic curve tails to be stubborn or unpredictable, so it’s great to see this steady downward trend continue right through to this end of the curve!

Notes:

This graph tracks both daily cases and reported deaths over the second wave. The axis for the cases is on the left, and for the deaths it is on the right and, of course, on a much smaller scale. The reason we have them both in the same graph, even though the numbers are so different, is to highlight the difference in timing between new cases and deaths.

There is on average a week’s lag from someone developing symptoms and being tested and counted as a case, and then developing serious enough illness that might require hospitalisation. It might be a further week before they require intensive care (ICU). Some people can remain in intensive care for a very long time; some might succumb to the virus even without being in ICU. But, on average, there will be a two to three-week lag between peaks in cases and the peak in the deaths that are the terribly sad consequence of those large numbers of new infections.

Cases started to plateau at the end of July, and we saw sustained high numbers for a couple of weeks before the case numbers started to fall in the second week of August. The numbers of reports of deaths finally also started to plateau in mid-August and, whilst fluctuating, has been reasonably stable since; averaging about 15 deaths a day. As we are now at the end of the month, it is expected that we will soon see daily reports decline, and the 7-day average with them. Because the day to day reports can fluctuate a lot, we also show the 7-day average so that you can see the trends over time.