Spread of Covid-19 in New Zealand would best be managed through a series of small and controllable peaks to ease pressure on hospitals, the country's top health official says.
To date, officials have been stressing the need of "flattening the curve" – or pushing out the demand on health services over time, rather than overwhelming them at once with a peak that could come with a mass outbreak.
But today, Ministry of Health director-general Dr Ashley Bloomfield said even a flattened peak would still overload the health system.
While there's yet no evidence of community transmission of Covid-19 – New Zealand's tally of confirmed cases stands at 20 and the ministry puts the risk of outbreak at "low to moderate" – some models have suggested numbers may take off over coming weeks.
"If you think about this as a single wave of transmission, you can model it – and all of the models show, yes that's what will happen," Bloomfield said.
But some more recent modelling that had just come though the Prime Minister's chief science adviser took a different focus of preventing a single, large peak.
"What we have done to date has been talking about flattening the peak. But even if you do that, you are still likely to exceed your health system capacity.
"So therefore, our approach is – and this is what successful countries have done – is you want to have a series of small peaks over a long period of time."
"You amplify up with quite stringent controls to make sure you don't exceed your health system capacity, and then as it goes down, you can ease those and be prepared to ramp them up again."
Bloomfield said New Zealand hadn't yet seen the initial peak – and measures to date had bought the country some time to look at what was working overseas.
"The challenge, here, and it's one I think we've risen to really well, is you need to think about what is it we think we might need to do in two weeks' time – and you do it now."
The health system was continuing to brace for the possibility of community transmission.
"The pandemic is going to place extra load on health resources with the extra complexity of infection and the need for isolation, not to mention the problem of healthcare providers becoming infected and needing to be isolated and recover," said Dr Michael O'Sullivan, a healthcare operations research specialist at the University of Auckland.
"Other services, such as elective surgeries, may need to take a back seat to coronavirus treatment in the short or medium-term. I think careful planning and hard work are going to be needed for New Zealand's health system."
O'Sullivan sad flattening the curve would lessen the demand for treatment resources like negative pressure rooms, or spread it out over a longer time period.
"This means that utilisation of these resources will be more manageable and it will also enable health practitioners to get time to recuperate and refresh."
Dr Ayesha Verrall, a senior lecturer at Otago University's Department of Pathology and Molecular Medicine, said treatment for coronavirus tended to be supportive, with no specific antiviral medicine available to shorten the illness or reduce its severity.
"The main support people need is with their breathing, either oxygen delivered by a thin tube to their nose, or if that isn't enough their breathing can be supported by a machine that breathes for them called a ventilator," she said.
This type of support could only be given in intensive care units by highly specialised staff.
Verrall said data so far also suggested people with Covid-19 had longer stays in hospital than for other infections.
"Mild cases might stay for a week, and severe cases for a couple of weeks or more."
A stocktake was underway on the number of ventilators in New Zealand, which had fewer than 170 intensive-care unit beds, but did have other facilities with ventilators like post-operative areas which could potentially be used.
Stopping elective surgery was another option to make sure there was flexibility in the system, Bloomfield said, and private hospitals were also being contacted to see what capacity they had if necessary.
Community-based assessment centres to run routine testing were being set up around the country, five of which would be open to patients in Auckland this weekend.
Behind the scenes, officials were preparing for the "manage it" phase of the national pandemic plan.
Under this phase - assuming multiple clusters of the virus was spreading out of control – authorities could consider the need for an epidemic notice, or declaring a state of local or national emergency.
Distribution of critical goods and services around the country could be prioritised by Civil Defence.
As demand in a moderate to severe pandemic was likely to exceed the supply of hospital beds, public and private hospitals, too, would need to prioritise admissions and "rationalise non-acute services and review staff rosters", the plan stated.
The capacity to admit people to hospital during the "manage it" phase was likely to be limited during a mild to moderate pandemic - and "considerably constrained" during a severe pandemic.
In the fifth phase - in which the wave was decreasing, but the possibility of a resurgence or new wave remained - authorities would move toward restoring normal services, re-opening schools, lifting restrictions on travel and public gatherings, and implementing vaccination programmes.
The final phase focused on recovery and rebuilding population health – and included the option of setting up special recovery offices.
Meanwhile, researchers at the Imperial College of London have explored two possible ways that public health officials could combat Covid-19 – with neither offering a rosy picture.
Their model, using the US and UK systems, looked at mitigation, which focused on slowing but not necessarily stopping epidemic spread, and reducing peak healthcare demand while protecting those most at risk of severe disease from infection.
The other was suppression, which aimed to reverse epidemic growth, reducing case numbers to low levels and maintaining that situation indefinitely.
Each had "major challenges", they said, and any one intervention by itself wouldn't be enough.
They found that taking some harder mitigation policies – that included combining home isolation of suspect cases and social distancing of the elderly and others at risk – might slash peak healthcare demand by two thirds and deaths by half.
"However, the resulting mitigated epidemic would still likely result in hundreds of thousands of deaths and health systems - most notably intensive care units - being overwhelmed many times over."
That meant suppression – minimally requiring a combination of social distancing of the entire population, home isolation of cases and household quarantine of their family members - would make for a better option.
The downside was this approach would need to be maintained until a vaccine became available – something that could still be 18 months or more away.
One adult died at the scene and three people suffered minor to moderate injuries.