Coronavirus: Up to 12 cases of COVID-19 expected each week at border

New Zealand can expect to see between four and 12 cases of COVID-19 recorded at our border each week, a modelling expert suggests.

After 24 days of no cases being recorded in the country, many Kiwis were surprised last week when nearly every day one or two cases were reported in our isolation facilities. That's despite a previous warning from the Prime Minister and Director-General of Health that we would see more cases due to the pandemic accelerating around the globe.

University of Auckland Professor Shaun Hendy, who provided modelling of the SARS-CoV-2 virus' impact in New Zealand to the Government, agreed that seeing more cases is expected.

"The border has always been a big risk and it is going to continue to be a big risk for us going forward. This is not over. We are only a few months now into this pandemic and we have got another year or more to go. We are always going to be focused on the border now.

"We probably should have been seeing one to two cases a week at the border. Maybe now, travel volumes have gone up, maybe we might be seeing four to 12, something like that, per week. That's based on the prevalence of the disease overseas and also where our travellers are coming from."

Currently, only Kiwis and their close families can enter New Zealand and must spend at least 14 days in a managed isolation or quarantine facility. The measures have become especially important due to few domestic restrictions in light of no community transmission being detected. 

"Most of the people coming in are coming from Australia, and although there has been this second outbreak in Victoria, numbers are still pretty low in Australia. People coming from Australia [are] relatively low risk. But still, people coming from the US, the UK, Europe, we have still got to be cautious," Prof Hendy told The AM Show. 

There were concerns about our border measures last week when it emerged two people weren't tested before being allowed out of managed isolation on compassionate leave. They tested positive for the virus days later. The Government has promised to fix the system and began by suspending compassionate leave exemptions. 

According to Worldometers, 9.5 million cases of the virus have been recorded worldwide, with 483,000 people dying of the illness. The United States has about 1.3 million active cases while Australia has around 500.

There have been surges in cases in some spots which have begun loosening their restrictions.

"We are seeing some parts of the world that had locked down and then are releasing some of their lock down. That is particularly apparent in the US, where they are relaxing some of their restrictions, but they have done that too soon," Prof Hendy said.

"It is almost just a continuation of the first wave. It is the disease spreading across the country and getting into populations which haven't had it before."

New Zealand - which only has 10 active cases - has had 22 COVID-19-related deaths since the pandemic began. That's compared to tens of thousands in other countries. A similar fate was initially projected for New Zealand if we didn't introduce strict lockdown restrictions.

Prof Hendy, who helped make those projections, said we could still see a large number of deaths if we don't keep on top of restrictions. That's also because most people don't have immunity.

"That's still a possibility. We haven't got widespread immunity in New Zealand. In fact, there are very few parts of the world where the disease has really infected a large proportion of the population. We are still seeing relatively small infection rates as opposed to numbers. We're all still vulnerable to the disease. We still have to be cautious, we can't write this disease off."

At the moment, he believes we have probably eliminated the virus.

"I think we can say we have probably eliminated it here. We have still got these cases at the border and that is always going to be the case, but we have probably eliminated, or very certainly eliminated, it internally," he said.

"We have got to keep up those border restrictions for a very long time. Last week was alarming. Compared to our changes in alert levels, relatively low risk. We have got to keep that up for a long time. A low risk times a long time period actually means a high risk, but over this long period. What we do at the border has to be sustainable, it has to be really tight and we have to get it right. But we do have a little while to work on that and get things as tight as possible."

A trans-Tasman travel bubble has been thrown in doubt this month as Australia saw an outbreak in Victoria.

"A lot depends on what happens in Australia. They didn't go for as hard a lockdown as we did and they are still seeing bubbling community transmission. For the rest of the world, we are going to have to wait until there is a vaccine. It is still spreading rapidly around the rest of the world," Prof Hendy said. 

We could see travel with Australia "early next year, later year, six months or so", but the rest of the world will probably be closed for a long time to come. 

Sweden is one country taking a herd immunity approach, keeping segments of society out of lockdown to slowly build up people's defence to the virus. It's had 62,000 cases and more than 5000 deaths. But it's believed the number with antibodies against the virus remains small.

It's chief epidemiologist Anders Tegnell is reported as saying on Thursday that it appeared the world had gone crazy and had forgotten everything experts had discussed prior.

Prof Hendy says the country has a long way to go.

"In Sweden, they have got a long way to go to herd immunity. This herd immunity strategy where enough people in the population have immunity to the disease. We still don't know, after you have had it, how long will your immunity persist. That is a big unknown at the moment. 

"It has to actually pass through a large percentage of the population before you have immunity within the community. Sweden has got a very long path to go before the disease actually comes to a halt there."