Predicting scenarios amid infection spikes informs critical public health decisions

Having eased back on all restrictions, WA needs to take the Melbourne COVID-19 runaway outbreak as a wake-up call and remain poised and ready to act within hours – with rapid response and road block teams on call and booze-bus-style COVID testing ready at hand, says UWA disease modelling expert Professor George Milne.

His message, after months of testing worst-case COVID-19 scenarios for the Western Australian Department of Health using a virtual, simulated computer model of Perth, is “it could happen here”. If it does, he says the speed and aggressiveness of the reintroduction of labour-intensive testing and disruptive social distancing measures will be critical to preventing a second wave.

Community-wide education should begin now to ensure the WA public is prepared well in advance to play their part, Professor Milne said, ready to cope with suburbs being quickly locked down and newly-gained freedoms wound back.

Commissioned to work with WA’s COVID response team, Professor Milne’s research team’s simulation computer model can provide a rapid understanding of the potential effectiveness of a range of quickly introduced new social distancing measures. These would have the ability to “knock out” a sudden COVID-19 outbreak in Perth while keeping the economy going, including interventions as precise as closing down just two suburbs.

The UWA computer model has already been used in Western Australia and Queensland in recent months to advise local health departments on the best social distancing measures to “flatten the curve”, the need for hospital and ICU beds and ventilators, gauge the level of asymptomatic cases, determine how to wind back social distancing without causing a rebound in cases, and where to increase testing.

Findings from the UWA model have also provided other countries currently with low- and high-level virus transmission with optimal staged and evidence-based strategies to safely exit social distancing. These have been shown to balance workplace return and community interaction without a rebound in COVID-19 cases over the next nine months, with study results published in MedRxiv. The study demonstrates the necessity of holding robust social distancing in place for as long as 14 weeks until COVID-19 virus transmission has significantly decreased and the importance of a staged relaxation of social distancing, even in lower transmission countries such as Australia.

"When WA opens up its border we will have to learn to live with low levels of virus transmission and we are probably going to get cases bubbling up."

Professor George Milne

“While WA has eliminated coronavirus infections, when WA opens up its border we will have to learn to live with low levels of virus transmission and we are probably going to get cases bubbling up,” said research leader Professor Milne from UWA’s Department of Computer Science and Software Engineering.

“We will then need to quickly determine where these cases are located, trace their contacts, test them and, if necessary, enforce home isolation. We need to get a message out to the wider public that it is important to have a robust response and to do it quickly.

“Areas in WA might have to be targeted and quickly locked down and I think that’s preferable to locking down the entire State - catching it early and locking suburbs down earlier until you eradicate viral transmission. 

“We may need to prepare government messaging for the WA public on the importance of home isolation, and testing to detect infectious cases that may not exhibit illness symptoms. These asymptomatic cases can lead to the “silent spread” of the COVID-19 virus, which the UWA computer simulation model is able to gauge using its “virtual world” of individuals whose movement and changing contact patterns is captured on a day-by-day basis, and assumes that a third of those who become infected are asymptomatic.”

Professor Milne said he believed Victoria had waited too long before acting aggressively on its outbreak and high COVID-19 infection counts in New York and the United Kingdom were lessons on what happened when a robust response at the start of the pandemic was delayed by as little as two weeks.

“Now that Australia is no longer in lockdown and restrictions have eased, determining how best to respond to a spike in cases is quite subtle and complicated.

“Our UWA computer modelling technology allows us to identify where people will become infected  — in the household, in specific workplaces, in the wider community — and that means we can reduce where that contact is occurring using various social distancing measures and determine where testing is most needed.”

Developed quickly at the start of the pandemic by Professor Milne’s team to guide Australian public health authorities, it is an adaption of an established UWA seasonal influenza disease model based on a 270,000-strong population in Newcastle in New South Wales and uses COVID-19 transmission data from Hubei Province in China collected before containment measures were activated.

“What has happened in Victoria is a series of unfortunate events and it is very important that other states can learn from it,” Professor Milne said. “We need the  causes and reasons to be made generally known so that if this happens in another state, and if the government takes severe measures in response to a new outbreak, then people can understand why.”

“But the real challenge will still be down the track when Australia feels it needs to open up to the world, possibly allowing travel with low-spread countries.”

This story is part of the series Computer modelling COVID-19 spread critical to flattening the curve.