Wider testing will reveal true Covid-19 risk

Without active testing in the community our Covid-19 picture isn’t complete, an epidemiologist says. David Williams reports.

There are worse places to be self-isolating than Whakatāne, in the Bay of Plenty, says Bridget Robson, who lives on a two-acre block and keeps chickens.

“We live in a beautiful part of the world, we’ve had lovely weather, and we can go outside while still being in our bubble.”

But the environmental management specialist is worried about the system of checking up on those, like her, who, having arrived back from overseas, are more likely to have coronavirus.

“It relies enormously on trust and while a lot of New Zealanders are very trustworthy, not everybody is.”

Robson and her partner arrived back in the country on March 19. Three days later they were joined by her partner’s daughter, who also flew back from overseas.

Authorities have called Robson three times now, her partner had their first call on Thursday, but her partner’s daughter hasn’t been contacted at all.

That doesn’t fill Robson with confidence the monitoring measures will be effective. She thinks others might have had to check into a hotel room, or similar, and will be miserable.

“The incentive to not stay in place would be much higher. And the capacity for someone checking is very, very low.”

On Wednesday, Director-General of Health Ashley Bloomfield acknowledged authorities couldn’t check all returning travellers, telling the Epidemic Response Committee that the vast majority of people understood their role and complied. Police abandoned plans to physically check on each new arrival.

The Government has so far resisted calls from experts to enforce a mandatory quarantine on those flying back from overseas. (Today Bloomfield said 135 people who had symptoms on arrival were in quarantine, while 1405 people without an adequate isolation plan were in managed accommodation. Thousands of others are in mandatory self-isolation.)

The Government’s now relying on increased testing to provide a clearer picture of community transmission.

University of Otago professor of epidemiology Michael Baker welcomes expanded testing, given that, until now, it has focused on people arriving back in the country. “Everyone acknowledges we need a lot more data and it needs to be analysed and presented in ways that can start to tell us about levels of risk around New Zealand.”

“My understanding is there is a high likelihood that some of the cases locally have been community transmission.” – Jim Boult

One place at greater risk, it seems, is Queenstown, which the virus has turned from a bustling tourist resort, teeming with overseas visitors and workers, into a locked-down ghost town.

The latest case data shows the Queenstown-Lakes district is the biggest Covid-19 hotspot, with 53 cases (well ahead of Dunedin’s 37), in the district health board with the most cases – Southern, with 131.

Already, there are 29 confirmed cases from the World Hereford Conference held in Queenstown early last month. And two nurses at the local Lakes District Hospital have tested positive.

Queenstown Mayor Jim Boult says: “My understanding is there is a high likelihood that some of the cases locally have been community transmission.”

The intent of the national lockdown is to extinguish chains of transmissions. But people are breaking the rules, including partying backpackers and people jumping off the Albert Town Bridge, near Wanaka.

Boult doesn’t think those gatherings are isolated cases, but is confident the message is starting to get through that they’re unacceptable.

“My message to those folk is that all New Zealanders are putting themselves through enormous social and financial pain to enable this lockdown to take place, and the intention is that we beat the disease and we stamp it out through that suffering that we’re going through.

“And if we’ve got a few idiots out there who give us the middle finger and continue to congregate and risk transmission that just is completely unacceptable and they need to get a life.”

Stay calm, keep testing

The confirmed cases to date probably happened before the lockdown, Boult says. “We’re monitoring things over the next few days to see whether any of the more recent cases are community transmitted. Of course, after we get past the 14 days of self-isolation we shouldn’t be seeing any community transmission cases. That’s our hope.

“It doesn’t surprise me, though, that we’ve got some community transmission, simply because we are a district that’s had a high exposure to overseas people and naturally we’re probably going to be more susceptible to that form of transmission.”

Boult’s not hitting the panic button. He believes health authorities are on top of the issue for now, and keeping the community well-informed.

Queenstown’s assessment centre for Covid-19 testing is at the local Memorial Centre, one of 62 around the country. With testing criteria broadened to include people with symptoms without a link to overseas travel or being a close contact of a confirmed case, the number of tests will increase.

On Thursday, the Southern DHB said it averaged 199 tests on people each day in the previous week. On Wednesday, it performed 333 tests and capacity is now 450 a day. There has been a commensurate increase in national lab tests. The Health Ministry is heading rapidly towards 5000 lab tests a day. Yesterday, 3446 tests were processed, with capacity rising to 5400 a day.

“For a country of our size, that’s a pretty good basis for telling us what’s happening,” epidemiology professor Baker says. “The critical thing is where are those tests being done, and who’s getting them. That will tell us the national picture.”

“The absence of positive cases doesn’t mean anything unless you know how many tests are being done.” – Michael Baker

Baker says the Ministry has focused on the acute response to infections, and the next phase is trying to stamp the virus out. “The data will be vital to that.”

Tracking the virus requires authorities to provide data on how much testing is being done in the community, where that testing is being done, and where the positive cases have been found.

Fundamentally, Baker says, surveillance is done to identify people who have the virus so they can be isolated and their contacts followed up.

“The number one reason for doing this is to contain and eliminate the virus. So that’s the goal. And the second thing it does is it gives you vital intelligence – information about where the pandemic may be spreading in parts of New Zealand.”

The picture to date, presented as a cumulative total of cases, is telling us little about the current risk of the virus spreading, Baker says. To have a functioning Covid-19 surveillance system, a certain volume of people across the country need to be seen and tested.

“The absence of positive cases doesn’t mean anything unless you know how many tests are being done.”

New Zealand is relatively long – imprinted on a map of the United States it stretches from northern Florida to about New York City. Given that broad geographic spread, Baker says that, even for our small size, this country has to do proportionately more testing to get an accurate picture of the virus’s spread.

When will we have a more complete picture of the Covid-19 risks? Baker says that depends on the distribution of the testing. “What I’d hope for, and many people would hope for, is that detailed distribution of test data and the results of test data, that’s what we really need to get this picture.”

Baker is careful to say he welcomes increased testing – the key in some Asian countries to containing the infection – and isn’t being critical of any agencies. “All those things they’re doing at the moment are taking us in the right direction, so I’m very positive about where we’re going."

From Whakatāne, Robson says the response to Covid-19 resembles something akin to a duck on a pond – “on the surface it’s smoothly swimming along and underneath its feet are going like mad”.

She’s about three days from graduating from self-isolation to plain old lockdown. Things in Whakatāne are very calm, she reports. “We’ve got room to get outside and talk to the chickens. We always talk to the chickens – they’re nice.”

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