New Zealand was a week away from a Italy-style "health system meltdown" because of Covid-19 just days before the decision was made to lock the country down.
The revelation is contained in a startling letter by Royal New Zealand College of General Practitioners medical director Dr Bryan Betty, where he also warned it would take just several infected people several days to cause a "potentially exponential increase in cases again".
Betty sent the letter to GPs on Thursday night. In it, he praised their work in confronting the virus and helping avoid a crisis.
"New Zealand has done incredibly well to avoid a Covid-19 crisis, which I believe is in large part due to general practice," he wrote.
"We've stepped into a world where the normal modern medical defences – vaccines and antibiotics – are not at our disposal.
"We've had to confront this (currently) untreatable diseases in the same way our parents and grandparents once faced other viruses – by practising physical distancing and good hand hygiene."
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Betty, who sat on the Ministry of Health's Technical Advisory Group which had oversight of the Covid-19 national response, said that on March 21, the country was nearing crisis.
"There is no doubt that when the College put the call out to switch to remote service delivery ahead of the lockdown it was the right thing to do.
"At that point (Saturday, March 21) we were literally a week away from not being able to contain the outbreak.
"We would have been faced with a potential health system meltdown like Italy, Spain, the [United Kingdom], and the [United States].
"The fact we avoided that is a credit to ourselves, the general practice profession. The College and general practitioners really stepped up to the mark."
Betty also outlined what had been learned about the disease over the past three months, including that the average age of death globally was 80 years; that co-morbidity was a major risk factor, especially diabetes, cardiac disease and immuno-compromised patients; and that a rare but worrying inflammatory condition in children had emerged.
But he also advised against being complacent.
As of Friday, New Zealand has had 14 days without any new cases, and there is just one current active case remaining.
"Although we have made good progress it would be remiss at this point to rest on our laurels and think this is finished," Betty wrote.
A large part of preventing another outbreak would be keeping borders closed, as the majority of Covid-19 cases here were introduced from overseas travellers.
The virus was running "unchecked" in many places around the world, and could "very easily" be reignited here if the borders were not secure.
It would take just three to five patients with Covid-19 to continue normal business three to five days to face a "potentially exponential increase in cases again", he wrote.
"We're treading a thin line between maintaining the gains we've made and relapse, and we need to be vigilant to ensure this doesn't happen.
"Personal protection, distancing and hand-washing are our main protections."
He urged general practices to continue to be leaders in this space, warning waiting rooms could act as conduit for the disease.
It was still a long way to go before the danger passed.
There were three ways it could end, he said, a vaccine was produced, herd immunity reached, or Covid-19 "burns itself out".
"Covid-19 has been an alarming experience and one we cannot back away from.
"A vaccine at best estimates is 12 to 18 months away.
"We all hope it will be sooner but that would be a miracle of modern medicine.
"Once we have a vaccine, it will take time for New Zealand to access it and immunise the population.
"If there was a second wave in NZ we need to be prepared to step up again.
"At this point we have won, but we need to keep that victory going."