Second wave, ripples or flare-ups – what next for the pandemic?

Predicting disease outbreak has been compared by more than one weary scientist over the years to weather forecasting. You don’t know exactly how big the storm will be or when it will hit, but you know it’s coming.

In late 2019, the hurricane came to shore: a new kind of coronavirus never before seen in humans quickly morphed into the worst pandemic in a century. Now it seems the skies are clearing, cases are easing and the world is waking up from lockdown. It’s time, as the Prime Minister says, for Australia to come out from under the doona.

Yet experts warn the storm is far from over.

The global case count is still accelerating and is expected to reach 6 million by June. While science is moving at its own record speed, there is still no vaccine or known treatment for COVID-19. And fears are growing that countries inching out of coronavirus hibernation to rescue their economies could trigger a dreaded second wave of infections, such as the resurgence seen during the 1918 Spanish flu.

In Australia, Deputy Chief Medical Officer Paul Kelly is duly on his guard, but he says our success so far in cutting off outbreaks quickly means we might see “ripples rather than a tsunami”, particularly with borders still closed for “the foreseeable future”.

Health Minister Greg Hunt has warned the biggest threat now, as states roll back restrictions, is complacency – piling into the pub too early and forgetting the virus is still with us. “We remain an island sanctuary … but the world is not out of the woods yet,” he says.

So if things aren’t quite back to normal yet, how long is the pandemic expected to go on? And how likely is a second wave?

How prepared is Australia for a second wave?

Right now, in the eye of the COVID-19 storm, Australia’s coronavirus wards are quiet. One of them, a pop-up hospital built in just 37 days on a cricket pitch in Canberra, may even be quietly dismantled without ever seeing a patient before the year is out.

The healthcare disaster mapped out in early epidemiological models three months ago has not come to pass in Australia – at least not yet. Professor James McCaw is among the experts at the Doherty Institute in Melbourne working on such models for government and says that, while Australia has so far avoided the devastating crush of COVID-19 cases seen in hospitals in other countries, he winces when he hears an Australian speak of the pandemic in the past tense. “We are still at the very start of this,” he says.

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The danger is perhaps just harder to see here. It has become as invisible like the the virus itself, epidemiologist Dr Craig Dalton says, because state and federal leaders acted on those models and their worst-case scenarios – under tough restrictions imposed on public gatherings and socialising, climbing caseloads plummeted before they could overwhelm hospitals. Just weeks earlier that curve had looked very different, with cases doubling every three to four days.

“People can’t see what [was avoided]; they would have been even more fatigued by shutdowns if they happened earlier,” Dalton says. “But I think probably if we left it even a week later, it could have been much, much worse – disastrous.”

The measures have bought Australia time. Stocks of life-saving ventilator machines have tripled. Extra staff are being trained in intensive care. Testing has been ramped up to one of the highest rates in the world. And, alongside other early leaders in the COVID-19 fight such as South Korea and Taiwan, Australia now has an army of disease detectives finding and isolating cases mostly imported from overseas.

Even large clusters, such as those spawned by the Ruby Princess cruise ship debacle in Sydney or the Cedar Meats outbreak in Victoria, have been stopped before they could spiral out of control, McCaw says. “We think we’re finding most cases,” agrees Professor Bill Rawlinson, who heads NSW’s biggest COVID-19 testing lab in Sydney.

Of course, while authorities feel confident they are on top of the virus, that doesn’t mean it has gone away. In fact, Australia’s low infection rates could make it an unwitting victim of its own success, Kelly says, with a population less exposed, and therefore more susceptible, to the pathogen if a second wave takes hold. “But I’m more hopeful now that won’t happen.”

How is the pandemic expected to unfold?

In the US, top infectious disease expert Dr Michael Osterholm often says that a virus has its own “gravity” or momentum. If left to its own devices, it would burn through cities and towns until enough of the world’s population had recovered with virus-fighting antibodies in their blood to ward off another infection. This is known as “herd immunity” and the magic number is about 60 per cent – generally more than half of a population needs to be exposed to a pathogen before transmission slows.

No country is there yet. Even those now overrun with the virus, such as the US, have reached only about 20 per cent. That means every nation is still about as vulnerable as the other to as potential second wave, Kelly and McCaw say. Questions also remain about just how protected COVID-19 survivors are from reinfection.

During the great plagues of the past, people had little choice but to let their immunity to disease build naturally. Now we have modern medicine and vaccines to speed things up – but even the most optimistic estimates put a COVID-19 vaccine discovery and rollout at between 12 and 18 months away.

In analysis published by the Centre for Infectious Disease Research and Policy, Osterholm and other experts have predicted the pandemic will last between 18 months and two years. (“About the same timeline as a vaccine,” Dalton expects.) But the virus itself is likely to hang around even longer – to be beaten back over time through vaccinations or even perhaps to persist as a seasonal illness.

“I don’t see this thing going extinct any time soon,” McCaw says.

“Viral gravity” also means that, like the ocean, outbreaks can play out in waves – an initial surge of cases might peter out, only to peak again then crash back down in another torrent, and sometimes a third or a fourth, whenever the virus finds a fresh foothold.

The last time the world faced a pandemic of this scale, it was reaching the end of World War I. But it was the second wave of that strange 1918 influenza, known as Spanish flu, arriving months later that claimed the most lives. For Australia, the third wave in January 1919 (about a year into the pandemic) proved the most deadly.

During the influenza pandemics since, experts point out that all of them saw a resurgence about six months later, regardless of the season. Many, such as the 1957 flu pandemic and most recently swine flu in 2009, were even bigger than the first wave.

This is our worst-case scenario for COVID-19.

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“If we relax restrictions too much, we could get a huge second wave,” McCaw says. Still, he remains hopeful for the “slower burn” scenario that Kelly is banking on, in which outbreaks flare up in smaller and smaller numbers and are put out by contact tracers.

“Those cases we’ve just seen with the [infected] sailors in WA, they’re in quarantine now, but that could be a little ripple,” Kelly says.

Those outbreaks won’t be nothing. This virus is more than 10 times deadlier than seasonal flu and all of us will still need to be on our guard in a “COVID-safe world” for some time yet – working from home more often, avoiding crowds, attempting elbow bumps instead of handshakes.

“For us, eternal vigilance may be the price of survival – as my surgery tutor used to tell me,” Kelly says. “At least until we get a vaccine. There’s still a lot of hurdles for a vaccine – it’s not a sprint, but it’s not a marathon either. I don’t think it will take three or four years. If we get one soon, then all bets are off; it’s a totally different world we’ll be living in.”

But if humanity doesn’t get its shot of immunity before the pandemic burns out, Osterholm’s research also envisions a third scenario – of more pronounced flare-ups or “mini-waves” with their own peaks and valleys, that will probably require countries to restore social restrictions, at least here and there.

Are we already seeing the start of a second wave?

Early success stories such as Singapore, Germany, Japan, South Korea and even Wuhan, where the virus first emerged, have faced fresh clusters after the public health rules were relaxed and places such as bars and cafes reopened. Pakistan is now contemplating reinstating its own lockdown after cases doubled in the three weeks since it was lifted.

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But the World Health Organisation warns we are still in the first wave of the pandemic. If a second surge does come, experts expect it to arrive around the end of the year, probably over the Australian summer and as winter returns to the other side of the world.

Still the bug can flare up again at any time after it has receded, the WHO stresses, so we shouldn’t count on months to prepare for a second major wave either.

How worried should we be about a second wave?

Past influenza pandemics give us cause to be on our guard. During the 1918 Spanish flu, San Francisco acted fast, shutting down while other US cities were overrun. But when cases receded, it opened up – people even celebrated in the streets, tossing their masks in the air. A second wave hit but San Francisco resisted restoring the restrictions that had worked before, put off by a newly formed Anti-Mask League. By the end of the pandemic, for all its early progress, it ranked among the worst-hit cities in America.

Likewise, when the third global wave reached Australia, going on to infect nearly a third of us, NSW lifted its shutdowns too early and then delayed reinstating them for weeks, even as cases climbed, allowing the virus to take hold.

Resurgence is common in the pandemic records, but Kelly says the fear of a larger second wave is still tied to 1918 and how that virus travelled around the world. Some experts argue the strain even mutated between its first and second wave to become more infectious, before eventually evolving into a milder seasonal flu. This virus, the first coronavirus on record to break out into a pandemic, is more stable than the wild genetic code of influenza, and it behaves differently.

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At first, McCaw says, disease modellers around the world looked to the other two dangerous coronaviruses found in humans – SARS and MERS. But while both strains are more lethal, they are also less infectious and so never spread beyond a few dozen countries. Critically, Kelly notes, they are not known to spread undetected, without symptoms, in the way the new coronavirus (and sometimes flu) can. So most experts have instead retrofitted the behaviour of the new virus into existing pandemic flu models.

“That [initial] modelling we did in Australia was like the long-term climate change outlook,” McCaw says. “Now, we’re pivoting to a daily weather forecast [using] Australia data to look at local outbreaks.”

While some have questioned the scale of the disaster first predicted for Australia, McCaw says even the local data now suggests there would have been a catastrophic outbreak similar to that seen overseas if controls weren’t brought in.

“This is the same virus as everywhere else. We’ve seen what it can do.”

How do we know it’s safe to reopen?

In the vast jungle of data now growing around COVID-19, Kelly is watching one number in particular – the reproduction rate, which measures how many people on average each patient will infect. If we can keep it below one in Australia (as it is now), the virus will eventually die out.

Then there is who is getting infected and why. Fifty new cases arriving from overseas and going into mandatory hotel quarantine is not as big a concern for Kelly and his team as 50 cases scattered across Australia without a clear source. “That’s when people get nervous. That means it’s circulating in the community somewhere,” Kelly says.

At the Grattan Institute, Stephen Duckett is working on modelling to try to measure tipping points – when a cluster could break through containment efforts. Both Duckett and Dalton are especially concerned about large workplaces as more of us return to them. Kelly agrees good ventilation as well as hand hygiene will need to come more to the fore.

Work rosters could also be staggered, Duckett suggests, with cohorts of staff cycling through the office on alternate weeks and deep cleans in between. “That way if some of them need to [self-isolate], they’re already home for the next fortnight before their turn to go back in.”

Public transport may be all that stands between us and the traffic jams of our nightmares, but in the era of COVID-19 how do we avoid the peak-hour sardine crush without handicapping the whole network? Some experts suggest we follow the lead of Europe and the US and make masks mandatory on board, but Kelly says solutions around ventilation, passenger limits and staggered timetables would be more effective. Australia is not officially advising people to wear masks in close quarters as they are often improperly worn and can lend a false sense of security. But on May 29, after the National Cabinet again rejected the option of recommending masks on public transport, Chief Medical Officer Brendan Murphy said it was still reasonable for people to choose to wear them on board.

Dalton– whose early work on low-cost, commonsense interventions to stop the spread of COVID-19 earned him a shout-out from the White House and its adviser, Dr Anthony Fauci, in March – is now working on a paper examining reopening. He says relaxing the rules in relatively low-risk settings such as cafes with customer limits or outdoor dining is one thing. “But places like nightclubs, aged care, religious institutions, that’s where we’ve seen things go wrong [overseas].”

Duckett adds a few more to the list: “Football matches, music festivals, church choirs. They can all be ‘superspreader’ events.”

Will shutdowns come back if cases climb again?

Prime Minister Scott Morrison has so far batted away the idea of a return to lockdown as the pandemic unfolds (“It’s like the emu and the kangaroo – they go forwards, not backwards”) and Hunt has also said it is unlikely states will bring back restrictions. Instead, “ring fences” of containment can be rapidly set up around an outbreak, putting a local area into its own temporary lockdown, as was done to contain a large cluster in hospitals in Tasmania’s north-west in April.

But some experts say Australia needs a well-spaced and specific framework in which to measure the impact of reopenings, similar to Germany’s “emergency brake” that considers restoring restrictions if cases reach more than 50 per 100,000 people over seven days.

Bringing back wider lockdowns in Australia can’t be taken off the table, Kelly says, but it’s not part of the plan – which is to mostly reopen Australia by July. “But we’re going slow so we don’t have to say in a month, ‘Whoops, it’s out of control,'” Kelly says. “[So] we don’t have to take out the sledgehammer again.”

While states are now easing restrictions at different paces, “none are going dangerously fast”, he says. Some have already enjoyed consecutive days without recording a new case.

Australia did not opt to try for total elimination of the virus as New Zealand famously did with its own tougher lockdown across the ditch, but Kelly says it’s possible it could be wiped out if our national borders stay up (to all, perhaps, but our Kiwi neighbours under a mooted Trans-Tasman bubble of safe travel). “Though I’m still not using the E-word [elimination] yet,” he says.

Hunt has said hard borders will remain an important part of the nation’s COVID defence going forward and Kelly adds: “can’t imagine any time into the future we’ll be getting back to business as usual there”.

But at some point, he says, Australia will have to open back up to the world.

And the longer our lives are disrupted by isolation and economic upheaval, the more likely another wave of health problems beyond just COVID-19 will build, including suicide.

On the economic side of things, at least, analysis by MIT researchers suggests that social restrictions could actually help countries recover in the long term. US cities that locked down early and for longer periods during the 1918 Spanish flu pandemic had fewer deaths and healthier economies when it was over, as local industries were able to bounce back faster.

McCaw says our state and federal leaders listened to the experts in first imposing shutdowns and it probably saved thousands of lives.

“If it’s getting away from us, we’ve proven once we can lock down – I think we can do it again,” he says. “If it’s between locking down again or having a runaway outbreak, I know what I’d pick.”