The Zero Spread Game

Blog post by Professor Tracy Smart AO, Public Health Lead - ANU COVID Response
28 September 2020

As we pass the six-month anniversary of our first COVID-19 lockdown it's a good time to reflect on It where we are and what the path ahead looks like. Some of you may not have imagined that we would still be living in a COVID world six months down the track. I certainly did but what I didn't anticipate was how well Australia would manage the crisis, and that politicians would, in the most part, listen to health advice so willingly.

Victoria notwithstanding, we have done an excellent job as a nation, from the highest levels of government down to the majority of individuals who have heeded the public health advice. And I believe the things are starting to look even better in Australia. The outbreak in Melbourne is finally starting to come under control and borders are gradually reopening, making the hope of having free movement across most of Australia by Christmas seem much more likely. This is in stark contrast to the situation in Europe, where they are in the midst of their "second wave", and of course the US, which is still averaging more than 40,000 new cases and around a thousand deaths a day.

But where to from here - what should our strategy moving over the next 12 months? You may recall that early in the pandemic we heard that our strategy to combat COVID-19 was to 'flatten the curve', which was really the reason for our first lockdown and which we did extraordinarily well. Then we were told that out strategy was 'suppression', while the goal for NZ was 'elimination'. These terms can be confusing, so to try and explain the options and look at where to next, I've dusted off my old public health notes, including a seminal WHO bulletin by WR Dowdle from 1998 that describes the strategies to combat diseases.

  • Extinction - this means that the agent that causes the disease (virus, bacteria etc) has entirely disappeared from the planet. You don't hear about this option much, probably because no disease has ever truly been made 'extinct'.
  • Eradication - infections are no longer occurring anywhere in the world because the agent causing the disease is no longer circulating amongst the population. It may still exist, but only under controlled conditions such as in a lab. Smallpox is the most famous example of this.
  • Elimination - infections and/or disease are no longer occurring in a specific geographical area due to the measures employed to keep it under control, like vaccination and closing borders.
  • Control - disease control means that the incidence and/or effects of infection or disease are reduced to an 'acceptable level' through various measures. I interpret "suppression" as being another term for control.

In the early days, I thought we should be aiming for elimination like our cousins across the ditch. This may have been achievable but it would have come at a price. As well as our mandatory initial lock down we would have had to close our borders completely. Although officially our borders have been closed since March, people have continued to enter the country and have brought the disease with them. The consequence is that both Australian and New Zealand have been importing the disease. We have therefore not truly eliminated it in either country - we have really been practicing control.

So what does this mean for us? It effectively means that COVID-19 will continue to be with us in Australia for a long time. It also means that we should be focussed on maximising control (or as the Department of Health has called it "aggressive suppression") with the aim to reduce local community transmission to zero. Or as Dr Norman Swan puts it a "zero spread" strategy.

I like the 'zero spread' concept as it makes things very simple and provides a clear understanding of the role we all have to play. If we behave in a COVID Safe manner, have strong jurisdictional public health systems to rapidly respond when cases occur, and occasionally go under further restrictions if directed, we will get to a state where COVID-19 is circulating in such small amounts that we are seeing little to no spread.  

Zero spread is already the reality in most areas of Australia at present (ACT, NT, SA, Tasmania and WA) and people in those areas are now living relatively normal lives. Both NSW and QLD have experienced community spread in recent weeks but their respective public health systems have responded well and have gotten things under control. If we can move all of Australia to a similar position, continue to demonstrate good and healthy public behaviour, ensure that we have robust contact tracing, and develop secure and more humane quarantine arrangements, our lives and the economy will start to improve and we will be in excellent shape to weather the COVID storm. This may also allow us to expand our bubble across the Tasman and into the Pacific well before the disease is controlled in the rest of the world and well before an effective vaccine is developed and distributed.

But Australia-wide zero spread doesn't mean we will go completely back to normal. We will still need to be alert (but not alarmed) and behave in a COVID Safe way. This is less about following rules and guidelines, which have often proven difficult and sometimes contradictory, and more about taking a principles-based approach to keep ourselves and others safe. Being COVID Safe means you must:

It really is that simple. If we do reach a zero spread situation and these behaviours become our new normal we will have learnt to live safely, comfortably and productively in the COVID world.

Stay safe and remain positive, Tracy.