While daily community cases have plunged to the lowest point in almost three months, a spike in cases at the border is being labelled "remarkable" by experts. 

Yesterday there were 18 new cases detected in the community. That's the lowest number since October 1, according to epidemiologist Michael Baker, who said elimination of Delta is possible. 

But while the downward trend might be welcome news, another worrying trend emerged from yesterday's cases. 

The highest number of cases were detected at the border in more than a week – 16 – which Baker said was "quite alarming". 

On December 21 there were just five cases at the border, and on Monday there were 10. 

"Both the numbers … are of great interest because we've got two completely different Covid-19 threats and the way to manage them is completely different," Baker said. 

Five of the new cases at MIQ are of the Omicron variant, bringing the total Omicron cases detected at the border to 54. 

Among infected returnees are recent arrivals from Australia, the United States and the United Kingdom – all countries swamped by Omicron outbreaks that have put a dampener on Christmas. 

Baker said it's expected Omicron cases will increase at the border, but measures might have to be put in place if they increased by too much. 

"The concern is if Omicron cases get much over five a day, particularly if you're getting 10 plus a day, you'd have to look at whether numbers needed to be reduced," said Baker. 

"New Zealand has done this before, or you look at the pre-travel arrangements before getting on flights to see if more can be done to turn down the tap. 

"The worry is, if you're getting … 10 to 20 cases a day, then you're putting a big strain on MIQ." 

The ministry last night told the Herald that the positive Omicron results were the latest results on samples that ESR had run whole genome sequencing on. The fact the Covid-19 positive people had the Omicron variant was normally identified a day or more after their initial positive Covid result. 

Baker also suggested the Government could reintroduce a list of countries that are "high risk". 

But while a close eye is being kept on cases at the border, Baker believes eliminating the Delta outbreak in New Zealand is conceivable due to the downward trend in daily case numbers. 

"It's not impossible the virus might get eliminated entirely at this period. 

"None of us have expected that to happen but it's not impossible, given the huge effort by New Zealanders in getting vaccinated, following the rules ... and the added boost of summertime." 

Cases have been decreasing for days. There were 62 cases on Christmas Eve, 126 over Christmas and Boxing Day, and on December 27 there were 34 community cases. 

Yesterday, it dropped to just 18. 

Baker attributes low community cases to high vaccination rates, people complying with the rules, but also low testing numbers during the Christmas period. 

"It's no accident that the numbers are now being pushed right down," said Baker. 

The Ministry of Health said daily tests being carried out are low because of the statutory holidays, and because many centres are closed. 

The Northcote Community Covid Testing Centre during the Christmas break. Photo / Brett Phibbs 

The warmer weather is also said to be helping. 

"The virus has transmitted wonderfully indoors but not at all well outside," said Baker. 

"The good weather will be helping, [people are] opening windows up for ventilation and cooling and that really makes it hard for the virus to transmit." 

He also said it's encouraging that there hasn't been an "explosion of cases around New Zealand" during the holiday period, and he hopes the downward trend will continue. 

But he warned against putting too much weight on data from a single day. 

"The other thing is to never get fixated on a single day ... it's to look at the moving average, but the moving average is still tracking downwards so hopefully it will continue." 

The seven-day rolling average of community cases now sits at 48.3. 

Cases were reported yesterday in Auckland, Waikato, Bay of Plenty and the Lakes district. 

An infected woman in her 70s died at Middlemore Hospital at Auckland on Monday night. 

"Our thoughts and condolences are with the patient's family and friends at this deeply sad time," the Ministry said. 

The family has requested that no further details be released. 

Meanwhile, the ministry said the Omicron cases being announced daily are the latest results on test samples that ESR have run whole genome sequencing on. 

"This process takes a day or more to complete after a case is identified. This process can take up to a day to complete. Therefore the Omicron cases announced each day are not the same cases as those being announced as new cases at the border." 

It added that not every positive case returned a whole genome sequence. 

"Many of the results fail because the case does not have an acute infection. 

"The Ministry recommends media do not make assumptions or comparisons between new border cases and the number of new Omicron cases identified by whole genome sequencing." 

- by Miriam Burrell, NZ Herald