Measures to control the spread of Covid-19 need to stay in place - on and off - for 12 to 18 months, a professor who studies modelling data on coronavirus says.
The coronavirus outbreak is expected to start spreading more widely in the community from early next month, with the disease peaking in August.
Health officials are looking at how to prevent a big spike.
They say even flattening it could still mean the health system is overwhelmed and what they want is a series of small peaks over a longer period of time.
That could be done by ramping up stringent controls and then easing them as the numbers of sick people rise and fall.
Professor Shaun Hendy, director of Te Pūnaha Matatini, a New Zealand Centre of Research Excellence focused on the study of complex systems and networks, said the key was bringing down the number of people infected by each person who contracts the virus.
"We're getting a lot of data from overseas on how the virus behaves. We can put those numbers into our model and look how different strategies might play out in New Zealand.
"If we don't do anything a very large peak ... will come over the winter months."
Quarantining people who are sick, staying away from public gatherings and hand-washing all help, but to turn the level of infections from a "tsunami into a number of small waves" needs more aggressive action," he said.
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At present, one person with the virus infects about 2.5 other people on average.
"That is enough to produce this exponential growth in cases that we're seeing in Europe and the United States. What we need to do is bring that number down."
The key is to start isolating even healthy people, Hendy said.
"You can describe our strategy at the moment as trying to find all the people who are sick or might be sick and quarantine them.
"To get to the situation where we can actually bring numbers down, we'd actually need to quarantine ourselves even if we haven't got symptoms, and that's going to mean things like closing schools, closing universities, working from home and limiting our mobility particularly around the country.
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The restrictive measures need to stay - on and off - for at least 18 months, Hendy said.
"These are going to stay on until we've got a vaccine.
"We've really got to build up enough immunity in the people so the disease won't spread."
Hendy said relying on 'herd immunity' by letting the tsunami of infections occur would be devastating for the health system.
"A large number of people would die if we adopted that strategy."
Putting in place travel restrictions in any part of the country where community transmission - unrelated to overseas travel - was identified would make it possible to contain the spread.