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Toby Morris, The Spinoff
Toby Morris, The Spinoff

ScienceAugust 18, 2021

Siouxsie Wiles & Toby Morris: Delta makes this a new kind of challenge. But we can smash it again

Toby Morris, The Spinoff
Toby Morris, The Spinoff

We’re in level four lockdown for the first time since April 2020. And we’re facing a new sort of foe. Siouxsie Wiles and Toby Morris explain the task ahead.

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The whole of Aotearoa wakes today at alert level four after a single case of Covid-19 was detected in the community. We’ve had community cases of the virus before, but we haven’t been in this strict a lockdown since the early days of the pandemic. So what’s changed?

The delta variant 

Because so many countries chose to suppress or manage Covid-19 rather than aim for elimination, widespread community transmission means more infectious variants of the SARS-CoV-2 virus have evolved. One of those variants is delta. Yesterday morning, before the bigger news broke, we heard that the delta variant had transmitted from one room to another within the Jet Park quarantine facility. The rooms were on opposite sides of the corridor. All it took for the virus to move from one room to the next was for their doors to be opened at the same time for about 3-5 seconds four times. 

A recent study of mainland China’s first delta outbreak has shown that the incubation period – the time between the person being exposed to Covid-19 and testing positive for the virus – has shortened. People tested positive on average at around 3.7 days after exposure to the delta variant compared to around six days after exposure to the earlier variants. That means once a case is identified, the virus could have already jumped more widely — a likelihood not only that they have transmitted it on to someone else, but that person has, too. That’s why hard and fast is the right way to stamp out delta outbreaks. 

The other important thing the Chinese study found is that the first time people test positive with the delta variant, their viral load is roughly 1,000 times higher than people infected with the earlier variants of the virus. The PCR test is not of course a test for actual infectious virus particles. But when we put that information together with the data on how many more people are being infected within households and workplaces compared to earlier in the pandemic, it suggests people infected with the delta variant are shedding much more virus, at least early on in infection. And that fits well with the delta variant being more infectious.

New South Wales’s current outbreak started with one case 

Yesterday, New South Wales reported 452 new cases. Their current outbreak started in mid-June, when a driver transporting international air crew became infected with the delta variant. That one case has gone on to seed an outbreak that currently stands at more than 10,000 cases. Hundreds of people are in hospital people and more than 50 people have died. All that in just two months. That’s what happens when you have the delta variant and go slow and soft with your restrictions rather than hard and fast.    

Yesterday we learned that a 58-year-old man who lives in the Auckland suburb of Devonport tested positive for Covid-19. It’s likely he’s been infectious since last Thursday. He spent the weekend visiting the Coromandel. The good news is he was an avid user of the Covid Tracer App, which is helping the contact tracing team pull together a list of locations of interest. Keep an eye on the Ministry of Health website here

As well as tracing who the man might have infected, the other important investigation under way is how he got Covid-19. The sooner we find that out, the better. Genome sequencing was in train overnight and will hopefully help link this case to the border in some way. The worry is that he is just the tip of the iceberg with a bunch of transmission chains currently shooting off in all directions. I’m hopeful that there aren’t too many unknown cases out there already. With all the wastewater testing being done, I would assume we would have picked up an outbreak. But not all of Aotearoa is covered by the current wastewater testing so we could have missed it. 

We’ve stamped out Covid-19 before and we will do it again

To stamp out Covid-19 outbreak, we need to limit our interactions with others to break any chains of transmission. We know the delta variant is much, much more infectious. We don’t know how many other cases there might currently be out in the community. Taken together, that is why a move up the alert levels is necessary. Level four restrictions minimise the number of interactions we have with others. It’s the best chance we’ve got of quickly getting an outbreak under control. Rather a short, sharp lockdown, than the weeks and weeks of restrictions like New South Wales are experiencing. 

So, as we wake up back in our bubbles at alert level four, here’s what we all need to be doing. Don’t panic. If you haven’t been using the Covid Tracer App, take some time to write down where you have been and who you have been with over the last few weeks. If you have the app, you can add the information as manual entries. If you don’t use the app, start now. Yes, the best time to be using it was two weeks ago. But the second-best time is now. So, try to get into the habit. Keep an eye on the locations of interest published by the Ministry of Health.

If you aren’t an essential worker, stay home in your bubble. You can leave home to give care to those who need you, go to medical appointments, go to the supermarket, and to exercise close to home. If you need reminding why our bubbles are so important, Toby Morris and I have got you covered.

When you are out of your home, wear a mask. Even if you are vaccinated, wear a mask. Remember, masks are about protecting our families, friends, neighbours, and all the incredible essential workers who leave their bubbles everyday so we can stay in ours.

And please, get tested if you have any symptoms that could be Covid-19. That’s how we’ll find any chains of transmission and stop them in their tracks.

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