The first case of Omicron has been detected in New Zealand.
The new variant has had an immediate impact across the globe, with experts and health officials warning of "tsunami-like outbreaks" due to Omicron being highly transmissable.
"Omicron is spreading at a rate we have not seen with any previous variant," Dr Tedros Adhanom Ghebreyesus, director-general of the World Health Organisation, said.
In Australia, NSW hit its highest daily toll seen since early September, with the state government considering new lockdown options.
The UK recorded the highest number of confirmed new Covid-19 infections since the pandemic began; the EU has predicted Omicron will become the dominant coronavirus variant by mid-January; and South Korea is rolling out the country's toughest coronavirus restrictions yet as hospitals grapple with the deadliest month of the pandemic.
With travellers into New Zealand still required to quarantine, experts have weighed in on Kiwis should expect in the coming months as Omicron rapidly spreads across the globe.
How the experts reacted:
Dr David Welch, Senior Lecturer, Centre for Computational Evolution and School of Computer Science at the University of Auckland, said the main thing we don't yet know about Omicron is exactly how severe it is.
"Given the high prevalence of Omicron in many countries, including across Europe, it is no surprise to see a case arrive here at the border. The fact it was detected shows the system is continuing to work as intended."
"Nearly all the infections we are seeing now are in people who have immunity to previous Covid variants and so have a good level of protection against severe disease, including from the Omicron variant,'' he said.
"In Aotearoa, about 25 per cent of the population (all those younger than 12 and 10 per cent of the 12s and older) still has no immunity at all as they are unvaccinated and have never had Covid. This group is highly vulnerable and the working assumption of most specialists is that Omicron is as severe as previous variants. Breakthrough infections in vaccinated people can also cause severe disease, although at a lower rate than in unvaccinated people."
"Even if Omicron turns out to be less severe than other variants, and a reason to believe it may be is given in a new study, the fact it spreads so rapidly means hospitals and other health systems will quickly become overwhelmed without strong measures to contain it."
Leading epidemiologist Professor Michael Baker says that on its own, Omicron doesn't pose much risk as the case has been detected in quarantine.
"The significance for us is much different to every other country, as we are isolating everyone that enters New Zealand. This is the benefit of New Zealand sustaining its quarantine system at the present time,'' he said.
"I think the biggest decision confronting the Government now is what to do about the planned relaxation of border controls in January and February next year.
"It seems a logical decision would be to postpone the opening plan into February to give people more certainty and understand more about this variant. The home isolation plan was designed when we were dealing with the delta variant which is being well contained and keeping rates relatively low across the country. In that scenario, we can tolerate a less rigorous quarantine system."
He believes, however, that the Government should consider a delay in the reopening of New Zealand's international borders in early 2022.
Dr Dianne Sika-Paotonu, Immunologist, Associate Dean (Pacific), Head of University of Otago Wellington Pacific Office, and Senior Lecturer, Pathology & Molecular Medicine at the University of Otago Wellington said the variant has been spreading rapidly across the globe and it will be critical to keep it from spreading further.
"Although vaccination levels have increased across the country which has been encouraging, vigilance is still needed. Areas remain in Aotearoa New Zealand where there is lower vaccine coverage and we are still dealing with a serious Delta outbreak, with Covid-19 continuing to spread across the country."
"With the recent shift into the Covid-19 Protection Framework/Traffic Light system, more people will be interacting and getting out and about coming into close contact with each other, increasing the risk that this will promote and accelerate spread – especially for those who are vulnerable, including our children,'' she said.
"Children, tamariki and tamariki aged 5-11 years may not have access to a fully approved Covid-19 vaccine until January. In the meantime, we still need to keep them safe and protected from Covid-19."
"If fully approved, they will be the most recent cohort to be added to the Covid-19 vaccination programme. This means they will have had less time than others across Aotearoa New Zealand to get the Covid-19 vaccine – an equity focus with appropriate prioritisation with the vaccination roll-out will be important and critical moving forward."
Covid modeller Rodney Jones says Omicron is "going so fast" it could set New Zealand's coronavirus effort back months.
"Omicron is a lot more mild and we're seeing lower hospitalisations per case, but we're seeing a lot of cases. It's not as bad as early waves, but we're creeping up there," Jones said.
"Everyone is scrambling to catch up with this. Omicron is going so fast, looking at the cases in New South Wales, in three days they have had as many cases as they had in the first 48 days with the Delta outbreak. We still don't know a lot.
"A day or two ago I would've said no [to reconsider opening borders in January] but looking at the data we've seen today you may have to worry about that - the sheer volume and the speed it moves, even in vaccinated people.
"If you look at South Africa where they have lots of immunity from having lots of infections in the past, it is spreading so rapidly.
"This wave may not last because it moves so fast but it sets us back two months. It's a bit like snakes and ladders, just as we thought we were there we slip back down two steps.
"We just have to be adaptive and realise each outbreak is different. We can't look at the past, we have to work it out on the fly. Just as we thought we were going to have a great Christmas - we will - but will have this hanging over us.
"Omicron moves so fast day by day, we'll learn more over the next three weeks. We will know more about MIQ in the next few weeks."