New Zealand might need to close its border to the United Kingdom if cases of the new Covid-19 variant there continue to skyrocket, says a leading public health expert.
The comments come in response to news on Sunday of 31 new Covid-19 cases in managed isolation over the past 72 hours, with 11 of the new highly-infectious UK variant.
One case is linked to the South African strain.
"I am very concerned, and this is possibly the most dangerous phase we have been in since the August Auckland outbreak," epidemiologist Dr Michael Baker told the Herald.
The spike in cases, the largest seen in months, included 11 linked to a group of international mariners, however eight of these were linked to historical cases and just three were current.
Baker said reasons for the increase were quite obviously linked to more people returning to New Zealand, and many of them coming from places where the pandemic is out of control, including the UK and parts of the United States.
It also made sense the majority of them were of the new, more infectious strain, of which 19 had been recorded in New Zealand since December 13.
The new strain has forced the UK back into lockdown, amid fears its health system will become overwhelmed.
On Saturday, the British government reported the number of confirmed deaths had reached 80,868 - the highest in Europe and the world's fifth-highest pandemic death toll. A day earlier, the country's daily reported deaths had hit a record high of 1325.
"It is just law of nature that we will see more of that here, but that is what makes it such a huge risk to New Zealand," Baker said.
This meant the country needed to up its controls to match the risk, he said.
At the high end of these controls New Zealand could "turn down the tap" of international arrivals.
He spoke of a "traffic light system", where countries with no or low community transmission could be green, while places like the UK and parts of the United States would be red, meaning flights from there would be suspended.
Canada had banned flights from the UK since December 21 to keep out the new strain.
France, Germany, Italy, the Netherlands, Belgium, Austria, Ireland and Bulgaria all announced restrictions on UK travel.
"That's at the higher end, but we might get to a position where the risk is just too high and we need to suspend travel from those places for several months, until there is greater vaccine coverage or those travellers have been vaccinated," Baker said.
At a lower level Baker said every measure needs to be taken to ensure the current systems are all working the best they can.
The boost in cases would also be putting extra strain on managed isolation and quarantine facilities.
"We have had about 10 border failures in the past several months, so mistakes will happen and we need to plan for them. Now with this new strain the risk is just so much higher."
A person infected with the new variant might infect three people, as opposed to the old variant infecting two, meaning it would spread much quicker through the community.
What was happening in Brisbane, which is in lockdown after the discovery of the highly contagious coronavirus overseas variant in a hotel quarantine cleaner, could easily happen here, Baker said.
"All the freedoms we are currently experiencing could all be at risk if we don't respond with the same vigour - we only have to look to Australia.
"We know we could wake up tomorrow and there [could be] an outbreak and we [might] not know where it came from, and we have to go back into an intense lockdown."
This meant if there was a community outbreak the country might have to go straight to level 4 to stamp it out quickly.
From January 15 travellers from the UK or the United States bound for New Zealand will be required to get a negative test result for Covid-19 before departing.
But Baker said he was also concerned about the veracity of overseas testing before people boarded their flights there.
"It is very important we understand the limitations of testing, which may not be done in the same environment as here."
He suggested as part of the managed isolation voucher system something like including several days' isolation at an airport hotel before boarding their flight to New Zealand after a negative test.
In New Zealand people needed to stay vigilant, to scan and get tested and isolate if they experienced any cold or flu symptoms.
"If we go a few months without an outbreak people and the whole system can become complacent. People are probably thinking with news of the vaccine the bad news is behind them. There is a lot of good news, but it is still many months away, and in the meantime the risk to New Zealand has almost never been higher."
Duty Minister Kris Faafoi said given the cases were being detected at the border showed the systems were working.
"What is happening with Covid infection and the more transmissible variants showing up elsewhere around the world is concerning and, along with the numbers of cases being detected at our border, reinforces why the Government will continue to be vigilant in our Covid response."
The new and more contagious UK variant can be passed on easier than other strains of the virus.
However, there was no evidence at this stage that the length of the infection period was any different to any other variant of Covid-19 or that it made people sicker, a Ministry of Health statement said.
The ministry said people who had tested positive for the new strain were being cared for with the same high level of infection prevention measures as all Covid-19 cases.
"Infection prevention control protocols are in place for all staff and we can assure the public that there is no increased risk to the community," the statement said.
Meanwhile Brisbane will be in lockdown until at least 6pm (Australian Eastern Standard Time) on Monday after discovery of the new strain in a community case.
No new cases were recorded in Queensland today while New South Wales recorded three new cases.