A report out of the UK's Imperial College London has caused countries around the world to rethink their entire response to the Covid-19 crisis.

Today, the Ministry of Health's director-general, Dr Ashley Bloomfield, described it as being "very critical" to New Zealand's approach, which has pivoted from trying to "flatten" one big peak of cases, to trying to manage a series of smaller ones through certain controls.

Why has the report been so influential? Science reporter Jamie Morton talked to Professors Michael Plank and Shaun Hendy, and Dr Alex James, of Te Pūnaha Matatini, New Zealand's Centre of Research Excellence in Complex Systems and Data Analytics.

The Imperial College of London report has caught the attention of governments around the world. What does it say?

The team at Imperial used mathematical simulations to look at the choice between trying to suppress the epidemic and trying to mitigate its health impacts.

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Mitigation – or "flattening the curve" - would allow the disease to spread, but attempt to slow it enough so that hospitals can cope.

Their simulations showed that this would be very difficult, if not impossible.

They then looked at suppression, which aims to stamp out the spread as much as we can until a vaccine comes along - this relies on instigating control measures like isolation, quarantine, social distancing and school closures early on, before the spread takes off.

This graph in the Imperial College London report shows
This graph in the Imperial College London report shows "mitigation" strategy scenarios for Great Britain showing critical care (ICU) bed requirements. The black line shows the unmitigated epidemic. The green line shows a mitigation strategy incorporating closure of schools and universities; orange line shows case isolation; yellow line shows case isolation and household quarantine; and the blue line shows case isolation, home quarantine and social distancing of those aged over 70. The blue shading shows the 3-month period in which these interventions are assumed to remain in place. Image / ICL

This strategy seems to offer a better chance of not overwhelming the health system.

How have they informed their modelling and what impact has it had so far? Why are these figures reliable?

The Imperial model has been adapted from one that has been used to track influenza.

It is one of the most detailed models in the world, and has been developed to try to understand how effective these sorts of interventions are in fighting the flu.

This graph shows
This graph shows "adaptive triggering" where cases could be managed in a series of peaks over time by using controls like university closures and social distancing. New Zealand is looking to meet the Covid-19 crisis in such a series of managed peaks. Image / ICL

Their recent work has been adapted with data on Covid-19 from around the world.

But these are still only possible scenarios and there is still a lot we don't know about this disease including crucially how different control measures, like closing schools or social distancing, will affect the spread.

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So any model is an exercise in planning for a wide range of best-case and worst-case scenarios and everything in between.

How might it help the way we visualise Covid-19 hitting here?

Once it has arrived and taken hold, the spread of Covid-19 has followed very similar patterns in almost every country.

The modelling results from the UK gives us some likely scenarios that we can plan for here, to help predict the hospital capacity and the control measures we will need.

We are doing modelling here, so it is really useful for us to be able to compare and learn from work going on overseas.

The upshot of the report seems to be that, no matter what approach you take, the health system is going to be overwhelmed. That's something the Ministry of Health's Dr Ashley Bloomfield spelt out yesterday. Are there any positive take-aways?

Our best shot is to try and suppress the spread for as long as possible.

This will buy us time to see what strategies are most effective in other countries so we can try and mimic them here.

The longer we can keep the spread under control, the closer we might get to having an available vaccine or an effective treatment, and the longer our health system has to prepare.

Based on the lessons from it, what should New Zealand be doing right now?

We should all be closely following the Ministry of Health recommendations about hand washing and stay home if we feel ill.

If we see community transmission, that is, if we see a case that can't be traced to international travel, then we need to be prepared for suppression strategies, which may mean closing schools, universities and non-essential workplaces.

And as the WHO says, test, test, test.