New Zealanders can pat themselves on the back for hitting zero cases, but not get together for a party just yet, doctors and health experts say.
There were no new cases of Covid-19 reported yesterday for the first time in nearly eight weeks.
Epidemiologist Michael Baker said it was a great symbolic milestone.
But in his job one day did not count for much - it was all about the trend, he said.
"Internationally, people have consistently underestimated this virus in terms of its ability to be detected without transmission ... and its ability to cause large outbreaks," he said.
And those outbreaks could appear suddenly after silently brewing.
"If you have one new case that you've missed, it might take you four weeks to even know you have an outbreak. That's because exponential spread is initially very slow, it's one, two, four, eight and it might take five or six days between each of those generations," he said.
- If you have symptoms of the coronavirus, call the NZ Covid-19 Healthline on 0800 358 5453 (+64 9 358 5453 for international SIMs) or call your GP
When RNZ last spoke to GP Marcia Wallace, she was sending her children to stay with their grandmother - worried about infecting them with Covid-19.
Six weeks later they're home and Dr Wallace is a lot more relaxed - but not too relaxed.
"We're still not out of the woods. We've taken a step towards the opening of the woods but we're not out yet," she said.
She hoped people would see the zero case milestone as a pay off for the hard work so far, not as a chance to stop being careful and socially distancing.
GP and Māori health physician Sue Crengle said she noticed a lot less anxiety about the disease in her patients and she hoped there would not be complacency.
"We aren't able to assume that we don't have virus somewhere in the community," she said.
People needed to keep up their hand hygiene and social distancing but also look out for vulnerable members of the community, she said.
The Nurses Organisation kaiwhakahaere Kerri Nuku said all people who work in health should be proud of the zero case mark.
Dozens of nurses had contracted the disease, a side effect of being on the front line, and many more were exhausted, she said.
If hospitals were to fulfil their need to be ready for another surge in cases, they need to look after their nurses while there was a lull, Nuku said.
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