Thousands of students around the country are heading back to school this week as two south Auckland schools are impacted by Covid infections in teaching staff before their students have even had a chance to step into the classroom. 

Principals are bracing themselves for further disruption over the next few weeks as modelling predicts the number of new Omicron cases could hit 200 daily cases by tomorrow, doubling to 400 by the end of the week. 

A staff member at Ōtāhuhu College tested positive for Covid-19 and three other staff members are self-isolating, while Reremoana School in Wattle Downs has delayed re-opening by a week after all 27 staff members were deemed close contacts of a Covid-19 positive case. 

Ōtāhuhu College principal Neil Watson said it was the school's first case this year, but it wouldn't be its last. 

Omicron is already so "dominant", the Ministry of Health announced yesterday it will stop reporting the specific variant of new cases. 

The country recorded 91 new Covid-19 new community cases yesterday. 

Ten people were in hospital with the virus, none of whom were in intensive care (ICU) or a high-dependency unit (HDU). 

Of the 91 new community cases, 65 were in Auckland. 

Te Pūnaha Matatini modeller Dr Dion O'Neale said this week was likely to see an upwards shift in case numbers. 

"Almost every other place in the world that's had an Omicron outbreak's seen a doubling time of around three days. We'd expect New Zealand to be similar." 

Daily cases could jump to 200 by the middle of the week then double to 400 by the weekend. 

"So that means about 100 cases a day at the start of the week, around the middle of the week we're probably looking at around 200 cases a day, and then doubling to around 400-ish by the end of the week. 

"Maybe things will go badly - that will arrive on the Thursday or Friday, maybe things will go well and we'll make it to Sunday before we get to that level - it's that rough pattern of taking around three days to double." 

O'Neale told RNZ that even though not all current cases were being confirmed as the Omicron variant, modellers expected it would be the majority soon and were now making their calculations based on its behaviour. 

"Omicron cases grow faster than Delta and other variants, so we expect it to out-peak other variants and take over... it's safest for us to be assuming that a case that comes up is Omicron unless we know otherwise." 

He warned Omicron had a very fast incubation period, or latent period - the time between a person getting infected and the point they showed symptoms and became infectious themselves. 

Once a person realised they were sick, took action to get tested and their results were reported, it could be four or five days from the point of infection. 

"That's important to remember: the case numbers we're seeing at the moment, those are infections that are already baked in, that happened some time ago." 

This also means that patterns showing comparatively fewer people getting tested for Covid-19 in weekends or on public holidays skew the numbers: "That will affect how those case numbers grow in the short term," he said. 

Cabinet is today meeting to consider changes to the current border settings in the coming weeks after the phased reopening announced in November was put on hold when Omicron emerged. 

Prime Minister Jacinda Ardern is chairing the meeting remotely. Despite testing negative for Covid-19, she is still isolating after being deemed a close contact of a flight attendant infected with Covid. 

Yesterday Tourism Industry Aotearoa (TIA) urged the Government to update its plans for reopening New Zealand's borders because Omicron had changed the game. 

"The previous plan was developed to respond to Delta, not Omicron. If Omicron becomes endemic in New Zealand, there will be no health reason to keep our borders closed or to continue self-isolation or MIQ for international arrivals," TIA spokeswoman Ann-Marie Johnson said. 

She said New Zealand needed to reconnect with the world and that people were desperate to reunite with family and friends. 

For some including pregnant Kiwi journalist Charlotte Bellis who is in Kabul and unable to secure a spot in MIQ, the border reopening couldn't come soon enough. 

Grounded Kiwis spokeswoman Alexandra Birt said Bellis' plight had shone a light on the situation in New Zealand. 

"We know that this is not a new story ... this is what thousands of Kiwis across the globe are facing," she told Newstalk ZB's Mike Hosking. 

Bellis' story had reached various parts of the world and more people, as a result, had started to realise how strict New Zealand's border restrictions are.