At the dawn of the Covid-19 pandemic, Professor Michael Baker reached for a relatable analogy to describe to Kiwis the rocky road ahead.
The catastrophe then enveloping the world was like a violent earthquake that struck from nowhere.
In its wake would come a long train of aftershocks that shifted the ground each time.
The professor's prediction soon eventuated, with the Alpha variant spreading to more than 50 countries before it was eclipsed by the disastrous Delta.
Sixteen months, 221 million infections and 4.5 million deaths after Baker's forecast, at a Wellington forum last month, another renowned University of Otago epidemiologist offered his own metaphor.
In trying to illustrate the sheer uncertainty that leaders faced trying to craft long-term plans amid the unprecedented crisis, Sir David Skegg turned back to September 1939.
"Near the beginning of the Second World War, can you imagine if Churchill had been expected to provide a detailed plan on how he was going to defeat the enemy?" he said.
"How could he have known that Hitler would turn his troops on the Russians, or that the Japanese would bomb Pearl Harbour and enter the war?
"Nor can we pretend to have a detailed plan, as to how we will reconnect with the world over the next year or two."
And nor could we have known, at that very time, Delta had crept past our defences and begun the spread through Auckland.
Later that month, Skegg told a health committee that, far from things getting easier, it would only get tougher as fortress New Zealand faced having to let down its drawbridge to the rest of the world.
In a remote and virus-free country unencumbered by the ravages of the pandemic, Kiwis had spent six months enjoying what he called a "golden year".
This outbreak, now numbering almost 900 cases, was the global reality knocking.
Kiwis swiftly plunged into lockdown were soon asking how long it would be this time, whether we could ever resume life as we knew it before, or if the light at the end of the tunnel was even in sight.
Could we plan large events, book concert tickets, or expect that our kids would be able to finish their last few school terms of 2021?
When would the Covid-19 nightmare end?
Scientists tell us not to think in terms of months, but years.
March of the variants
Removed though we are at the bottom of the planet, New Zealand's future under the pandemic is wedded to that of the rest of the world.
And how soon we could hope to return to some form of pre-Covid normality depended not just on what course the virus took over the next two years, but how it responded to what we threw against it.
"Unfortunately, the unique features of this virus, and the unique components of our cells that the virus uses," Professor Graham Le Gros told the Herald, "means we cannot really predict just where it will go in a population of [eight] billion as interconnected and interdependent as we are today.
"We have never faced this sort of challenge as a global polity before."
The renowned immunologist and director of Wellington's Malaghan Institute explained that humanity simply hadn't reached a "steady state" with high rates of immunity, either from natural infection or vaccination.
If it was, then scientists might be able to observe how the virus was responding to the pressure of not being able to infect enough hosts, or how well our best vaccines were performing in this setting.
Instead, the tempo was being dictated by fast-spreading variants packing shorter incubation periods.
Even in countries with good vaccination coverage, doctors were recording more infection among young children, and more patients needing hospital care.
And for us here in Aotearoa, Le Gros said, we could now see that menacing variants like Delta could slip through border defences – and only be crushed with strict lockdown measures.
Baker said we were locked in the thick of an arms race against the virus, all while sailing through uncharted waters.
"This virus has the demonstrated potential to infect much of the world's population, kill 0.5 to 1 per cent of those infected, and leave some survivors with serious chronic illness - unless we put effective barriers in its path."
So far, some barriers have held up better than others.
The benefits of actively trying to squash the virus, or wipe it out completely, were shown in the pandemic's first year, just as those of mass vaccination have been seen in its second.
"Longer-term outcomes," Baker however added, "are less certain".
Many predictions made so far have proven overly optimistic.
One Cambridge University study, for instance, surveyed 140 experts in April last year about what the UK's death toll would number at the end of 2020.
Their median estimate was 30,000; the figure at December 31 was more than twice that, at 75,346.
But scientists have offered some rough forecasts about the trajectory.
Although the virus was evolving at a rate only about half that of influenza, its travels across the globe have rather quickly enabled it to evolve and better infect us – the troubling variant Mu being one of its latest incarnations.
Baker described a process of natural selection that wound on until the virus reached what's known as "maximum fitness" - and it was difficult to tell if Delta had arrived at that point.
Once vaccination rates have begun to really pick up around the world, it might be that we foster a selective advantage for variants more resistant to vaccine-induced immunity, while perhaps not as effective at killing us or making us sick.
Or, Baker said, it might be that the evolutionary path leads to variants with nastier traits, like spreading faster, overwhelming immune defences more easily, and inflicting yet more death.
"This pattern appears to be what we are seeing with Delta."
He turned to a now oft-cited report by the UK Government's Scientific Advisory Group for Emergencies (SAGE), which explored four specific scenarios around how the virus might evolve from here.
The first possibility was that a variant, as he mentioned, might emerge to cause severe disease across a greater proportion of the planet's population than has occurred so far.
This hypothetical super-variant could prove as potent as Sars-CoV-2's best-known predecessors – Sars-CoV and Mers-CoV – which carried case fatality rates of around 10 and 35 per cent respectively.
And it could arise through point mutations, by recombining with other host or viral genes – or even recombining with other variants being tracked by world health authorities.
One worrying danger was that two variants, each with different strategies for overcoming innate immunity, could merge to not only make the virus replicate more often, but inflict more sickness and death.
As long as the virus was continuing to circulate widely, there was a "likely" probability it could undergo such a genetic change – and there was also a "realistic possibility" that its severity would worsen, the Sage scientists reported.
But Professor David Hayman, an infectious disease ecologist at Massey University, believed the infection fatality rate wouldn't jump as high as that suggested, or at least not while the virus continued to spread so successfully.
"If it did happen, I think it would change the entire scenario in the region it occurred at least," he said.
"Anything with such high case-fatality rates, and even the most sceptical of people would take preventative measures, and I suspect control would actually become easier."
A second scenario in the Sage report was a variant that evolved to evade vaccines, virtually setting scientists' efforts back to January 2020.
This could be caused by "antigenic shift" - where the spike gene sequence of another type of coronavirus already circulating in humans recombined into the body of the Sars-CoV-2 virus.
Or it could result from "reverse zoonosis" - where humans infected animals with the virus before it bounced back to us.
In rare cases, that's already been observed in minks, cats, and rodents.
It meant that, in people with existing immunity from either getting the vaccine or having had earlier Covid-19 infections, the virus would appear as a completely new invader.
The Sage report said there was a "realistic possibility" of this playing out – and vaccinologists would need to attack the variant from a rapidly modified platform, just as they did last year.
Scenario three was a drug-resistant variant that emerged as a direct result of anti-viral therapies used against Covid-19 - a likely prospect unless these medications were used correctly.
And the final scenario was an arrival of variants that spread faster and became endemic, but which came with much milder infection in most people, just like human coronaviruses that cause common colds.
Hayman similarly couldn't see that happening any time soon.
"On current evidence, it looks highly unlikely in the short term, given the Delta variant seems to be not only more infectious, but also possibly slightly more pathogenic," he said.
"For something to replace that but be less severe, it would likely have to be more transmissible than this, yet also less pathogenic."
Rather, he expected scenarios two and three to be realised, to some degree.
"However, while I suspect some vaccine evasion and drug resistance are likely, I think it is unlikely that there will suddenly be a new variant to which the current good vaccines offer no protection at all."
University of Otago evolutionary virologist Dr Jemma Geoghegan also suggested several potential pathways for the virus, but nevertheless pointed out how tough it was to make predictions about future severity.
"It is complex - there are plenty of examples of viruses becoming more or less severe over time, and virulence isn't necessarily coupled with virus fitness."
For the foreseeable future, at least, she saw it becoming endemic.
"We might see seasonal peaks as fewer susceptible hosts will become available, coupled with waning immunity from vaccinations or past infection."
And even if it did eventually transition to something like influenza, that eventuality was far from ideal.
According to one recent study, flu now killed as many as 646,000 people each year.
Dr David Welch, a computational biologist at the University of Auckland, meanwhile shared a slightly simpler forecast: that Delta could likely become the only variant in town, within just months.
"While simple mathematical models suggest virulence decreases over time, this is not a proven fact and certainly doesn't tell us how things are going to change over the next five, or even 100 years," he said.
"What we do know is that Sars-CoV-2 is infectious enough that essentially everyone will get some sort of immunity to it, either through getting infected with it or by getting vaccinated against it."
Although this pattern had been seen in other coronaviruses, Welch added that it wasn't clear how virulent those were in the first place.
"It seems that this one may well be on the more virulent end of the scale and may well stay there."
Do vaccines spell victory?
Nearly one-third of Kiwis have now received the Pfizer-BioNTech vaccine – and Le Gros said immunity-priming technology like this remained our "best hope and only hope" in economically and efficiently waging war against Covid-19 in the community.
What stock could we place in shots?
Right now, the good news was that vaccines appeared to be working well enough to prevent excess deaths, or our hospital intensive care units from becoming overwhelmed – which they could easily be.
Already, an exhausted health workforce is stretched thin after redeployments to maintain record testing, vaccination and contact tracing rates.
New Zealand has fewer ICU beds per capita than other developed countries and in "normal" times hospital ICUs are often nearly full, particularly in winter.
The strain of this outbreak was even enough to test Auckland hospitals, which were forced to call in ICU nurses from elsewhere in the country and make last-minute changes to create more negative pressure systems.
The peril of Delta blasting through a mostly unvaccinated population was gravely highlighted by the fact that, of 90 people who've needed hospital care with Delta infections this past month, just one patient had received both doses, while 15 had been given one.
The bad news was that vaccines still weren't working well enough to block simple infection and transmission – something critical for gaining any population immunity from variants with short incubation periods.
Some studies are also indicating the effectiveness of the new vaccines could be gradually waning over time.
Quite simply, Le Gros said that allowing the virus to spread by easing restrictions would inevitably lead to some sickness and death – and the degree of which depended on vaccine coverage.
"Each country seems to be deciding what balance of restrictions versus morbidity their resources and cultures will allow."
Australia's national plan – to which disaster-stricken Victoria and New South Wales have been forced to retreat – aimed for an uptake of 70 to 80 per cent, albeit with continuing health measures.
New Zealand hasn't set such a goal, other than trying to vaccinate as many Kiwis as possible.
If regulators found the vaccine safe for use in children under 12, as it likely soon could be, experts say there is reason to use it.
"There is concerning evidence coming through now about the impacts of Covid-19 infection on children, for example potential effects on the developing brain," University
of Otago epidemiologist Dr Amanda Kvalsvig said last month.
"We shouldn't be exposing our children to risk from this new virus while these effects are not fully understood."
In the world of Delta, however, the prospects for liberation through population immunity were bleak.
One recent modelling study calculated this would require 98.1 per cent of New Zealand's entire population getting the Pfizer jab – a threshold not far off the 97 per cent that Te Pūnaha Matatini researchers earlier arrived at.
In the face of rampant social media misinformation about vaccines, surveys showing only around 80 per cent of Kiwis were willing to have the shot, and many other barriers, hitting that mark seemed fanciful.
And yet, even with sky-high rates of coverage, if New Zealand abandoned all of its public health controls and let Covid-19 wash through the population, the modelling predicted more than 1000 people could die in the space of two years, while 11,400 would need hospital care.
Le Gros said the world's focus urgently needed to be on developing a next-generation vaccine that gave better coverage for all variants, along with long-lasting immunity, so that countries could begin to staunch the cost and harm of Covid-19 for decades to come.
If one was found, we might even dare to imagine a global eradication campaign, as had succeeded against smallpox.
"However, the difficulty with Covid-19 - unlike smallpox and rinderpest - is that the coronavirus is not wholly dependent on humans for its circulation, and could always return to infect unvaccinated people in decades to come," he added.
"One thing that has always been clear is that we have to live with viruses and limit the disease they can cause – trying to conquer them is not realistic."
Our new normal?
So what will our new future look like?
At the same forum where Skegg made his Churchill reference, Prime Minister Jacinda Ardern outlined plans for a phased reopening of a highly-vaccinated New Zealand some time in 2022.
She sketched out a "pathways" system of travel, where entry into New Zealand would depend on factors like whether a traveller had been vaccinated, and whether they'd been in any high-risk countries in the fortnight before.
If the traveller had received their jab and had come from somewhere where the virus was circulating but which still had good vaccination rates, they might not need to do a full 14 days in MIQ, but either a shorter stint or a period of home isolation.
Alongside this approach – which would ease hot demand for MIQ spaces – new digital tools would track travel data, and new rapid testing could be rolled out at the border.
"Our ultimate goal is to get to quarantine-free travel for all vaccinated travellers," she told the forum.
For a crippled tourism industry, in which four out of 10 jobs were lost in the space of just a year, the return of international visitors would be welcome.
Yet, less than a month after the PM's speech, Covid-19 Response Minister Chris Hipkins told Parliament this week that the Government's thinking around country-risk profiling was already shifting, with Delta having "changed the game".
Delta now meant someone could pick up Covid-19 and become infectious within 24 hours, he said.
"Now, that all plays into a question mark about what our medium- to longer-term border settings will be," he said.
"We haven't set out any new thinking on that."
Already, some experts have suggested that our former bubble-buddy Australia would have to become a designated medium- to high-risk country if the virus spreads across the rest of the continent.
But, all the while, the Government was still looking at pushing ahead with a small trial for vaccinated business travellers arriving here.
For Kiwis themselves, "vaccine passports" to fly abroad could be in place by year's end.
At the start of this year, these were being hopefully trumpeted as the key to unlocking the world.
But, as the University of Auckland's Professor Tim Dare noted, they've hardly featured in any recent attempts to manage the virus.
"It's become clear that even the best vaccines don't provide complete protection, and certainly for countries pursuing elimination, that's a reason not to think being vaccinated will settle whether it is safe to let people return to normal."
As well, the general concept of these passports – which are also being required in some countries to access crowded indoor venues - still raised tricky equity issues, given some people simply wouldn't be able to vaccinate.
"We will need to ensure that we provide support to make sure they are not significantly harmed if they cannot qualify for a passport," Dare said.
"One worry is that existing inequalities will grow, as some people are able to return to their normal productive lives while others cannot."
It's not clear whether these would become part of our society in the medium term, although academics like Dare have now spelt out the clear problems inherent in the concept.
Neither is it clear for how much longer that masks will be required on buses, trains and flights, or that many businesses will need to ask customers to scan or sign in – measures now part of alert level 1.
What the Government has made clear is that in the short term at least, New Zealand won't be abandoning its hardline elimination stance, and will be rapidly moving to kill off outbreaks when and wherever they were found.
Skegg said high levels of vaccination should make it easier to stamp out clusters of Covid, while acknowledging that new variants like Delta would make that task all the more difficult.
If we chose otherwise?
He offered a grim cautionary tale of choosing otherwise: the UK's ghastly experience.
Even with 94 per cent of English adults carrying antibodies from vaccination or past infection, and even with many people wearing masks, avoiding social contacts and working from home, England registered 649 Covid-19 deaths over the last week of August.
Equivalent to New Zealand's population, that came to nearly 60 deaths a week.
Baker, similarly, couldn't see any logic in giving up on elimination - a status we were likely to return to within weeks.
"This position gives us the ability to see how different strategies are working in the real world, rather than having to largely rely on modelling and previous experience with other pandemics," he said.
"We can, in particular, see how SARS-CoV-2 behaves in highly vaccinated populations such as Israel and the UK.
"These observations can tell us a lot about what 'living with the virus' might look like in key areas such as health, personal freedoms, and economic impacts.
"The experience of these countries will help us answer critical questions about impacts such as the incidence, severity and duration of long-Covid."
All of this knowledge, he said, was needed to make an informed choice about the relative benefits of different long-term strategies for managing Covid-19.
In the medium term, the elimination playbook might mean relying on a combination of high vaccination and a well-oiled test-and-trace apparatus to stamp out any flare-ups, with reduced reliance on lockdowns.
Annual Covid-19 booster shots, as we have for seasonal flu, have also been tipped, but experts told the Herald that all depended on how the virus changed.
"For flu, the vaccine is remade each year with a different virus because the flu viruses evolve to escape the immunity," Hayman said.
"It's not clear Sars-CoV-2 evolves like that but it still seems unlikely. That's not to say there might not need to be booster vaccinations if immunity wanes, or new vaccines against novel variants in the future."
And that all pointed back, again, to a global crisis that only a global effort could address.
"This pandemic, as well as global climate change, are both demonstrating the interdependence of countries and populations," Le Gros said.
"We haven't been able to convince ourselves of this fact, so it looks like mother nature is doing it for us.
"In the long run, the best way for our countries to have healthy and successful economies and populations is to face the fact of our interdependence on each other."