June 17, 2020

Alert but not alarmed?

As you know, two people were allowed out of isolation in Auckland, travelled to Wellington, and subsequently turned out to be positive for SARS-Cov-2.

On the one hand, this was definitely not the administration’s finest hour.  Mistakes were made, and while I don’t think firing people at this point is very productive, I hope someone is finding out who all made them and ensuring they don’t get made again.

On the other hand, even if everything happens the way it should, people will, from time to time, come out of border isolation carrying SARS-Cov-2.

We expect that one or two cases will be arriving in New Zealand each week, and while the testing and quarantine process will catch the majority of these, the tests are nowhere near perfect.  It’s quite possible for someone to arrive with a mild case of the disease, and pass it on to someone else in quarantine, who is still healthy and still tests negative when they leave.  It’s going to happen.

The imperfectly closed border is why the COVID tracer app is still useful: we want to have some way of keeping track of where we’ve been and when, to speed up contact tracing.  It’s why staying home is important if we’re at all unwell. It’s why testing is important if we have any plausibly COVID symptoms. It’s why… one of the reasons why… handwashing is important. And it’s why kindness is important; if people are scared to get tested because of public reactions, we’re going to be in trouble.

If most of us mostly do things right, the contact tracing system can cover up the unavoidable gaps, and we can have rugby and pubs and universities and dating and KFC. But there’s still a pandemic out there.

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Thomas Lumley (@tslumley) is Professor of Biostatistics at the University of Auckland. His research interests include semiparametric models, survey sampling, statistical computing, foundations of statistics, and whatever methodological problems his medical collaborators come up with. He also blogs at Biased and Inefficient See all posts by Thomas Lumley »

Comments

  • avatar

    Strict isolation within quarantine is hardly infeasible. I would have hoped that protocols would be tight enough that the risk would come from the small proportion of very long incubation periods or from false negative test results rather than from someone leaving quarantine catching it from someone entering quarantine.

    4 years ago

    • avatar
      Thomas Lumley

      In a sense, it *all* comes from false-negative test results: if we had a really good test, we wouldn’t need quarantine, or would need a much shorter duration.

      There could be more isolation, but I’m not convinced that strict isolation of children, for example, is feasible.

      4 years ago

  • avatar
    Dale Smith

    yes agreed, that’s why I find it disappointing that in going to level one, most of the hand sanitiser stations have also disappeared from many shops/malls etc.

    We have quickly reverted back to old habits.

    Suddenly the crowds are back. just as we come into the virus season.

    The methodology we are using is not a long term sustainable plan. Is this going to be the response to every outbreak?

    4 years ago

    • avatar
      Thomas Lumley

      At least now one can easily buy one’s own hand sanitiser and masks and so on.

      I think the government is still working on surveillance design. Like everything, it’s been done on a just-in-time (or not-quite-in-time) basis.

      4 years ago