Victoria's coronavirus modelling says stage 4 lockdown and restrictions should stay in place in Melbourne for weeks - ABC News

Victorians have been anxiously waiting to see the State Government's plan to emerge from the one of the world's toughest lockdowns.

With businesses shuttered, students learning remotely and socialising banned for weeks, many were hoping stage 4 restrictions would end on September 13, as originally scheduled.

But modelling produced by experts from the universities of Melbourne and New England, and released by the Victorian Government, paints a bleak picture.

Health officials are now warning Melburnians may remain in stage 4 lockdown until mid-October.

Here is the Government's modelling report:

Around the world, countries are struggling with the pandemic. Some have never emerged from their first wave

• COVID-19 has caused 26 million global infections and 1 million deaths
• Many countries have never emerged from their first wave
• Early action in Victoria enabled control to be quickly regained

COVID-19 has had a tragic impact on people around the world.

To date over 26 million have been infected.

Almost a million have died.

In many countries the virus was allowed to spread for weeks, or even months, before containment measures were put in place.

Stratospheric levels of demand for intensive care occurred and much could not be met.

In Victoria, cases peaked at just 104, of which 48 were acquired through local community transmission.

Some of these people will live with permanent disability arising from COVID-19. 20 lives were tragically lost.

Modelling published in April showed the much more catastrophic outcome that would have happened in the absence of intervention.

58,000 Victorians would have been infected on the worst day of the pandemic. 10,000 would have needed intensive care. Many would have died.

The 14-day new case average in Brazil, Canada, Mexico, Russia, the United Kingdom and the United States. Source: Our World in Data (2020). Note: These countries have increased their testing capacity, meaning their first and second waves are not perfectly comparable.(Supplied: Victorian Government)

For the latest news on the COVID-19 pandemic read our coronavirus updates story.

Other countries have emerged from their first wave but exited restrictions too quickly, and are now experiencing resurging infections

• Victoria is one of many countries now experiencing a second wave
• Most have arisen from countries exiting restrictions too quickly
• Many countries that aggressively suppressed avoided a second wave

Victoria has recently experienced a second wave of infections. Outside Australia, New Zealand, and Taiwan, which have pursued aggressive suppression and elimination strategies, these have been common.

Second waves have typically occurred following premature easing of restrictions, with jurisdictions underestimating just how challenging it is to maintain control with even low numbers of infections.

Examples of resurgence include:

Israel, which gained control over new COVID-19 outbreaks after their first wave in April. But schools were opened on May 17, which soon led to outbreaks in classrooms that spread to homes.

Spain, which used stringent stay-at-home orders until May. In June, restrictions were removed, and international tourism was encouraged. This soon led to a second wave. European countries have since banned travel to Spain. Its hospitals are reaching capacity again. And provinces have just been given the power to re-enter lockdown.

France, which after strict lockdowns in March and April is now facing a second wave. Masks are being made compulsory. Some schools remain closed. Local lockdowns are being considered. A national lockdown has not been ruled out.

The 14-day new case average in Belgium, France, Ireland, Israel, Italy, Japan, South Korea and Spain. Source: Our World in Data (2020). Note: These countries have increased their testing capacity, meaning their first and second waves are not perfectly comparable.(Supplied: Victorian Government)

Stage 4 restrictions enabled Victoria to turbo-charge its exit from Wave 2

• Less stringent Stage 3 restrictions have proven ineffective in Victoria
• Moving to Stage 4 more than doubled the rate of decline in cases
• Staying in Stage 4 longer means total exit from restrictions sooner

Thanks to the incredible sacrifices made by Victorians during Stage 4 restrictions, we are beginning to suppress the spread of coronavirus.

Stage 3 restrictions helped slow the growth of coronavirus cases, but even with masks, cases were taking 49 days to halve.

The introduction of Stage 4 restrictions helped us speed things up, and cases are now halving every 18 days: more than twice as fast.

Keeping Stage 4 restrictions until case numbers are low enough to safely reopen will enable all Victorians to get back to COVID-normal, faster.

The Victorian 14-day new case average.(Supplied: Victorian Government)

Read more about coronavirus:

Victoria will not be in a safe position to re-open in mid September

• On September 4th, we had a 14-day average of 116 cases (1,624 total)
• In mid-September, we will have an average of 63 cases (882 total)
• With so many cases in the community, re-opening at this point will risk a resurgence, undoing all of the gains achieved from lockdown.

Coronavirus can quickly get out of hand, and the national strategy to make sure we do not have 1,000s of daily cases is to suppress community transmission.

University of Melbourne modelling finds that it is unlikely we will have aggressively suppressed the virus by mid-September.

Based on current levels of social distancing, the 14-day case average is likely to be around 60 cases by mid-September.

By contrast the worst fortnight that NSW has experienced outside of Stage 3 restrictions was 13 domestic cases per day on average.

If restrictions are eased while the virus is still circulating widely in the community, there is a real risk that infections will rebound — causing restrictions to be reimposed and last much longer.

The Victorian 14-day new case average. The UniMelb DPM model begins on September 3, and 14-day averages are only available from September 17.(Supplied: Victorian Government)

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Aggressive suppression is our best bet for avoiding a yo-yo effect

A yo-yo effect is where lack of control is achieved, causing restrictions to be continuously lifted and reimposed. The University of Melbourne model suggests that if we ease restrictions when there is a fortnightly daily case average of 25, there is a 6 in 10 chance of having to lock down again before Christmas.

Ultimately, a wide range of different scenarios could play out over the coming months in Victoria.

Our exact path will depend on policy decisions, how well Victorians can follow public health advice – and luck.

There are strong elements of randomness in how SARS-CoV-2 spreads throughout a community.

One person who is infected with the virus might be very infectious to others, for a long time, and have lots of contacts before they are told to isolate.

Another might have few contacts or be less infectious.

Running a large number of model simulations tell us what is most likely to occur.

In 640 out of 1,000 model simulations, reopening too early (at 25 cases per day over the fortnight, on average) causes a yo-yo effect.

The below graph shows just 1 these 640 scenarios.

The cases fall and restrictions are eased slightly, then significantly from when the fortnightly average case numbers hit 25 cases per day (350 cases total).

Cases soon start to rise, and restrictions need to be tightened again before Christmas to avoid a large third wave that overwhelms the health system.

An indicative simulation of easing at a fortnightly average of 25 cases a day (14-day new case average). In the first section, restrictions are eased partially in the lead up to a 25-case average, then significantly at 25 cases. In the second section, restrictions are tightened. In the third section, restrictions are eased at 25 cases.(Supplied: Victorian Government)

Appendix

Authors:

Melbourne University's Dynamic Policy Model (DPM) is the result of an extensive international collaboration among a multi-disciplinary team from Australia and New Zealand over many months.

Primary contributors are:

• Dr Jason Thompson from Melbourne University's Transport, Health and Urban Design Research Lab
• Professor Mark Stevenson from Melbourne University's Transport, Health and Urban Design Research Lab
• Professor Tony Blakely from the Population Interventions Unit at Melbourne University's School of Population and Global Health
• Professor Rod McClure from University of New England's Faculty of Medicine and Health

Contributors in the project have generously given their time pro-bono to DHHS to provide outputs from their model.

The model:

The University of Melbourne's agent-based dynamic policy model (DPM) for COVID-19 imagines a simplified world where people (agents) move around like pieces on a chess board. Each person has their own characteristics. Some are old, some are young, some go to work and some go to school. Some are very infectious when they get COVID-19, and some are not.

If a person moves into the same square as another person who has COVID-19, they may catch the virus. People can reduce their risk by avoiding other people, keeping 1.5m distance or wearing a mask. If a person becomes infected and is traced by the health system, they are isolated and are less likely to infect others. As greater (or lesser) restrictions are imposed by the DPM, people change the way they move around the chess board — Following restrictions, some may stay at home more, or deliberately try to avoid interacting with others. If case numbers decline and restrictions are loosened, agents' mobility and interactions increase.

Agent based models are used throughout academia to model phenomena as diverse as economics, transport, and infectious diseases.

The DPM has parameters that are based on the disease mechanics of COVID-19, and have been validated against Australia and New Zealand's first and second wave of infections. This means that the model is helpful in predicting more likely outcomes of changes in social and health policies related to social contact and therefore, disease transmission.

This model has been peer-reviewed and published in the Medical Journal of Australia.

What you need to know about coronavirus:

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2020-09-05 19:21:00Z
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