Photo: RNZ
Keep testing and stay home if you're unwell is an expert's advice as thousands more cases are notified.
Latest figures show more than 6000 cases, that's double the number of cases from the week before and as of Sunday there were 314 Covid patients in hospital.
The hardest hit regions are: Canterbury, Counties Manukau, Waitematā and Southern.
The country is experiencing its highest peak in Covid-19 cases since December 2022, Professor Michael Baker told RNZ in late May.
Otago University Biochemistry Professor Kurt Krause said it was important to continue testing for Covid-19 so that health experts knew if the cases were "a ripple" or "a major wave".
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He believed a major outbreak was unlikely.
Kurt Krause Photo:
The data on cases also helped to protect vulnerable people in the community such as those who were elderly or had compromised immunity.
The latest strain was a distant Omicron variant. JN1 was the biggest strain at present with a few other minor strains which were closely related to it.
"It's just this continual drifting into new and different variants and combinations of Covid that we've been living through for the past three years.
"There's good evidence this latest strain is more contagious than previous strains but there really isn't good evidence that it's more dangerous than any of the other strains we've had."
Prof Krause said rapid antigen tests lasted about a year and it was not recommended to rely on expired ones.
However, some manufacturers had found old ones had lasted longer than they expected.
He recommended people keep a supply even though they will no longer be free after 30 June.
Asked what people should do if they suspected they might have Covid but a RAT test was negative, he said he would like a culture to develop that people stayed home if they were sick.
People should stay home to protect both themselves and their co-workers and if they needed to go out briefly wear a mask.
"Please stay home if you're sick."
People should also consider they might have another winter virus such as influenza-A or another respiratory virus.
"It's not just Covid out there."