Herald staff, Jordan Bond of RNZ 

The increasingly widespread use of rapid antigen tests has seen a sharp rise in positive Covid cases - and experts now expect New Zealand's Omicron peak to occur within a fortnight. 

And the peak in hospitalisations will occur another two weeks after that, says the Ministry of Health, meaning the country could be on a downward slide by late March/early April. 

But, according to modelling, active Covid-19 case numbers could already be as high as half a million, or one in 10 New Zealanders, with many unreported positive results and others asymptomatic. 

More than 23,000 community cases were reported on Thursday - 503 people are in hospital. 

Director general of health Ashley Bloomfield said just over 1 per cent of the population were active Covid cases for the period February 21-27. He again urged the 938,000 people who are eligible to receive their booster shot to do so. 

The Ministry of Health reported 23,183 community cases with the majority - 19,805 - detected via rapid antigen tests (RATs). 

University of Otago epidemiology professor Michael Baker said the availability of RATs meant New Zealand was now detecting more community cases that might have been missed previously. 

"If we'd been doing rapid antigen tests throughout, we might have seen a slightly gentler climb to the current level," he said. 

One in 10 could be active case 

Figures from Covid Modelling Aotearoa expect actual infections to be about four times the number of reported cases. 

There have been 146,779 confirmed active cases in the past 21 days. Some of these would have recovered. If the modelling is correct, that confirmed case number would indicate there have been around half a million actual Covid-19 infections in the country in the last three weeks. 

That is one in every 10 people. The higher rate in Auckland means it would be about one in five people. 

A tradie in Auckland says he knows about 25 people with Covid-19, none of whom have officially recorded their cases with the Ministry of Health. 

The tradesman, who did not want to be named, had seven or eight staff out at the moment - about half his workforce. 

"I asked the guys if they're going to report their tests, and they're actually just sick, they just want to go to bed. They don't want to sit online trying to work out how to log a case. It's just more admin." 

They could track most of the company's cases to two construction sites. 

"One particular construction site that a few of my guys were on is now just a ghost town. There's normally 60 or 70 people working there, and at the moment there's, like, five." 

Even people he knew in a personal capacity were not reporting tests. Knowing they had Covid-19 and what to do about it - isolate and have paracetamol on hand - seemed to be enough for them, he said. 

"I don't know anybody who's reported a case, and I probably know 25 people who have it. I think it's far more prevalent than the what is out there in the (Ministry of Health) case numbers." 

The man said all the cases he knew were isolating and following the rules, just not officially notifying their positive results. 

Peak on its way 

Bloomfield said the peak in case numbers was expected over the next week or two and hospitalisations were expected to peak two weeks after that. 

New Zealand's hospitalisation rate – calculated by the number of people in hospital over the number of current cases – was 3.5 per 1000 active cases, Bloomfield said. However, the number and rate was expected to rise over the next couple of weeks as hospitalisations lagged a week to 10 days behind case numbers. 

Baker said hospitalisations and intensive-care admissions were rising more slowly than case numbers. This was a key metric to observe, he explained, because it indicated a potential future burden on the health-care system and questions over whether there would be sufficient capacity to care for people. 

A blog produced by Baker and University of Otago colleagues Dr Jennifer Summers and Professor Nick Wilson in early February applied the peak hospitalisation and intensive-care figures in Australia to New Zealand on a per capita basis. 

Their analysis suggested peaks of 1107 people in New Zealand hospitals and 90 people in intensive care units. 

Baker said at least 100 people a day, based on our current Covid-19 cases, would eventually be admitted to hospitals. 

Yesterday's Covid-19 community cases were in Northland (520), Auckland (13,237), Waikato (1870), Bay of Plenty (1332), Lakes (537), Hawke's Bay (315), MidCentral (381), Whanganui (79), Taranaki (289), Tairāwhiti (134), Wairarapa (94), Capital and Coast (1487), Hutt Valley (642), Nelson Marlborough (271), Canterbury (1294), South Canterbury (53), Southern (615) and the West Coast (16). 

The location of 17 of the cases was not yet known, the ministry said in its 1pm update. 

Bloomfield said 54 per cent of yesterday's new patients were aged under 30 and 14 per cent were aged over 50, but the opposite pattern was being seen in hospitalisations. 

He said of the 345 people in Auckland and Northland hospitals, where the best data was available, and excluding those in emergency departments, 21 per cent were aged under 30 while 60 per cent are over 50. 

The average age of those in hospital yesterday was 53. Seven people were in intensive care yesterday. 

Strike postponed 

Meanwhile, a major strike which would have seen 10,000 health workers walk off the job today over low pay and poor working conditions has also been postponed. 

The first of two strikes was set to kick off at 6am today before the Employment Court halted the action by granting an interim injunction. 

Health officials also reported yesterday that one person with Covid-19 had died in a Bay of Plenty rest home. The person died of an unrelated medical condition while receiving palliative care and had tested positive for Covid. 

Separately, as Omicron spreads to dozens of aged-care homes in the country, a coalition made up of residents, workers and facility operators has written to Health Minister Andrew Little calling for urgent action over long-term nurse shortages that reached crisis point. 

Forty per cent of a rest home's staff could be stood down at any one time – which could potentially be "catastrophic" on top of current shortages, the letter said. 

Pay parity and a boost in training programmes were needed as the aged-care sector grappled with a shortage of 1000 registered nurses, or 20 per cent of the workforce. 

Meanwhile, 100 people have now been charged in relation to the Parliament protest's violent end on Wednesday and a significant investigation is under way to track down those who committed unlawful acts, police assistant commissioner Richard Chambers told reporters yesterday afternoon. 

Baker said the most "undesirable" aspect of the protest was the "gross misinformation" depicted on placards and signs that were then depicted in coverage and photos and subsequently shared with a wider audience. 

"It's a super-spreading event for disinformation," he said. 

Yesterday, 17,963 booster doses were administered throughout New Zealand and all of the country's district health boards have now had 90 per cent uptake of the first dose of the vaccination.