The decision to pause trans-Tasman travel is appropriately risk-averse in light of the devastation that the Delta strain could wreak in New Zealand, writes Marc Daalder

Analysis: Imagine if our Level 4 lockdown in April 2020 hadn’t worked.

Imagine if, despite the stringent measures and people mostly following them, the virus found a way to spread between people in their infrequent trips to the supermarket, along crowded hospital corridors, amongst port workers and truck drivers and everyone else involved in the supply chain.

This was a scenario the Government planned for. In early April, the Treasury dreamt up a worst-case scenario in which Level 4 was “insufficient” and the situation called for “a more extreme form of lockdown, for example a narrower definition of ‘essential’, stronger restrictions on movement, and deliveries only permitted for essential supplies”.

Food would be rationed. Volunteers would be rapidly up-skilled to take over hospital shifts as more and more health workers fell ill or refused to work. The Government would dictate the price of essential goods. Certain exports would be blocked and new capacity to manufacture critical items and PPE would be cobbled together.

This nightmare scenario didn’t arise. Level 4 was strong enough to eliminate Covid-19 and Level 3 was enough to re-achieve elimination when the virus resurfaced in August. But the high transmissibility of the Delta variant of the coronavirus would require stronger restrictions than Level 3 and might even put Level 4 to the test.

That knowledge is what drove the Government to shutter the trans-Tasman bubble for the time being. The Delta outbreak in Sydney has highlighted our worst fears – many of those testing positive for the virus have been in the community at supermarkets, pharmacies and health centres while infectious. This isn’t a case of rule breakers spreading the virus, but rather the rules themselves not being strong enough.

Even so, our Level 4 requirements still allow people to go to the grocery store or the doctor’s office. If Delta can spread in those venues in New South Wales, it could do the same here.

And while our contact tracers are excellent, NSW’s has been seen as “gold standard” in the region. A recent review of the February outbreak found our contact tracers “would struggle to maintain high system performance of contact tracing for a prolonged period with 100-200 cases per day” – and that’s based on each case having between 20 and 30 contacts. The Sydney case who visited Wellington in June produced 2600 contacts.

At that rate, even an outbreak of just a few dozen new cases a day would quickly stretch contact tracers to their limits.

This is not to say that Delta is unstoppable. With just a handful of cases and a clear and recent point of entry, a minor Delta outbreak could probably be corralled at lower alert levels with our existing contact tracing system. And the Government has pledged to be far more willing to impose restrictions in the event of community cases than NSW was when cases first popped up there in June.

When it gets dangerous is when the virus is able to spread undetected for several weeks. A recent study of a Delta outbreak in China identified that people tend to become infectious sooner after contracting the variant and have a viral load that is as much as 1000 times higher than with the original virus.

This means it is easier to transmit the virus, it will transmit to more people and those people will themselves be able to spread Delta more quickly. A couple of weeks of unmitigated spread could see us in the same straits as Sydney. By then, contact tracing would be playing several days of catch-up. In this scenario, the virus will be moving faster than we can test, trace and isolate it.

How realistic is this situation?

Victoria is now grappling with a small Delta outbreak exported from NSW, with 14 new cases today and 26 new cases yesterday. That’s despite the state having closed its borders to NSW just like New Zealand has.

Victoria acted fast to move into lockdown and most of the cases they’re finding were in isolation for their infectious period. But the situation would look very different if Victoria had been a little slower to trigger lockdown or if a few more cases had made their way into the state – and besides, New South Wales was confident their outbreak was under control at an earlier stage as well.

What is clear is that the New Zealand public is doing too little to help expose any potential outbreak. Daily scan counts are down to 623,000, after peaking at just under a million during the last Wellington Delta scare. Only around 330,000 New Zealanders are using the app to scan or put in manual entries on any given day – well below the 1.5 million people who have downloaded the app and activated Bluetooth tracing.

In other words, just 20 percent of those who have the app downloaded and Bluetooth tracing enabled are actively scanning with it. Add in the number of people who aren't using the app in any way and it becomes clear that we can't count on digital contact tracing to signficantly supplement manual efforts.

A similar complacency is visible in testing. Modelling commissioned by the Government after the August outbreak found that if 35 percent of symptomatic cases sought a test, any outbreak would likely be confined to 50 cases by the time it was identified. The Delta variant is likely to have raised that threshold, but we're far from meeting it.

Data from the latest report (which had 44,500 respondents) shows that about 1 percent of New Zealanders had a fever and cough last week. Of those, just 13.1 percent got tested for Covid-19 - and that's among participants who are probably more likely than the average person to be conscientious and get tested if sick.

This complacency will also have factored into the Government's thinking when it decided to close the bubble. While it's possible that stringent border measures and high community testing and scanning rates would have kept Delta out of New Zealand, the reality on all three of those fronts was far from desirable - recalling that, until recently, no more than half of pre-departure tests were being checked for arrivals from Australia.

Given the grievous risk of a Delta outbreak that spirals out of control, shutting off the tap from across the Tasman was the most prudent move.

Marc Daalder is a senior political reporter based in Wellington who covers climate change, health, energy and violent extremism. Twitter/Bluesky: @marcdaalder

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