Will flattening Australia’s curve be enough?

Australia’s approach to COVID-19 should do more than simply lengthen the pandemic to take the pressure off health systems. It must evolve into an attempt to either eliminate the virus, suppress it indefinitely or carefully control transmission, James Trauer and Emma McBryde write.

‘Flatten the curve’ has been a mantra guiding the Australian response to COVID-19 since shortly after the virus arrived in the country, and remains a widely accepted description of the current strategy for responding to this pandemic.

However, if this phrase simply means turning a peaked curve into a broader, longer epidemic curve, without action to eliminate, suppress or mitigate the epidemic, the result will be a catastrophe. Unfortunately, all possible longer-term responses to COVID-19 are associated with enormous risks and costs, but a ‘flatten the curve’ strategy that also lengthens the curve is among the worst of the options available.

If Australia had done nothing in response to the virus and were to continue to do so, most predictions suggest that around 60 per cent of the population would be infected by COVID-19 and up to one per cent would die. Health systems would be overwhelmed up to 20 times over and five to 10 per cent of the population would be simultaneously infected with the virus at the peak of the epidemic.

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These horrifying figures follow from our knowledge of the behaviour of the virus, including the fact that each person with infectious COVID-19 will infect on average about two and a half additional people. Since the start of the epidemic, there has been near-universal agreement that we must do everything we can to avoid this outcome.

But how many ways are there to achieve that? A strategy built around simply ‘flattening’ the curve, with no concern for its length, still implies a large, bell-shaped epidemic, but one with a lower peak than under the do-nothing approach. The initial rise would still be exponential, but the upslope would be gentler, perhaps implying that each infectious person infects on average one and a half additional people. What would this look like in reality?

Under this scenario, the epidemic peak is considerably reduced and at its highest point fewer than half as many people would be simultaneously infected. However, this could still represent three per cent of the population or nearly one million people in Australia. It has been acknowledged that this would overwhelm health systems, no matter how much effort is invested in scaling up hospital and critical care services.

But even more importantly, it would render a traditional public health response completely impractical. Even with this lower number of infected people, at the peak of the pandemic it would be impossible to identify all cases, test them and trace their contacts to ensure that chains of transmission were identified and people were appropriately quarantined. Unidentified chains of transmission would be everywhere.

If the government took this approach, then as the country headed towards a flattened epidemic peak, the only option remaining to slow the spread would be the blunt instrument of totally shutting down communities, including prolonged workplace and school closures.

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As long as each person is infecting more than one additional contact, the flatter it goes, the longer the epidemic lasts. Eventually, if it flattens to the point that the health system can cope, the epidemic may be so lengthened that it could last for two years, the whole period of which physical distancing would need to be observed. By this time there is hope that a vaccine could arrive to change the game.

There are three alternatives to this. One is to try to drive the virus to complete extinction and then seal national borders. Although this seemed impossible until recently, China’s success in hugely curtailing domestic transmission suggests that this may be possible.

However, if leaders take this pathway, policymakers, epidemiologists, and the medical profession need to start communicating that this is the goal to the population immediately. Australia would need to reduce case numbers to zero through an aggressive and sustained response, and then keep them there for several weeks to be sure that transmission has been completely halted.

Explaining the need for businesses to remain closed and society locked down in the face of a virus that has apparently vanished would require one of the greatest public relations campaigns in national history, and one which has not yet commenced.

Even if this approach failed for Australia as a whole, it could still work for isolated communities, regional towns, or even regions with favourable geography, such as the Northern Territory or Tasmania – with appropriate restrictions on travel – could be provided the freedom to choose this path if desired.

Complete suppression, which consists of trying to ensure that each infected person infects less than one additional person on average, is a second alternative. This response consists of driving down case numbers to a level that hospitals and health departments can cope with, and then trying to hold them there while gradually attempting to release the brakes on the system.

This may be the strategy that Australia adopts – and it may work, although it also comes with enormous risk. With this approach, testing and contact tracing strategies must first be optimised, so that authorities can be sure transmission is manageable before selecting the first brake to release.

As educating children is among the most critical processes to a functioning society, ensuring schools remain open may be the first brake Australia’s leaders choose. However, with the extent of transmission in children difficult to quantify, even this may be enough for the epidemic to rebound, leaving no alternative but returning to lockdown.

Although there is a third alternative of allowing some transmission while protecting the elderly and vulnerable, this strategy is also difficult. The only possible hope for this strategy lies in the very low fatality rates in children, such that sustained, controlled transmission in younger groups could be proposed as a means to gradually edge us towards herd immunity. Such an approach would have to be designed and executed with extreme care, and would be much more complex than merely partially flattening the epidemic curve.

Elimination, suppression and allowing controlled transmission could each work and could each fail, but none of these strategies represents merely ‘flattening’ a still-peaked curve. No matter what, Australia needs to choose one of these three paths and pursue it with a clear understanding of where it could lead.