Big difference in Covid-19 random tests in NZ and US

Street testing has been carried out in various parts of New Zealand and is not finding positive Covid-19 cases, which suggests the community spread of the virus is very low (although some claim we still insufficient data to make decisions about reducing lockdown restrictions).

All (about 340) tests processed  from the Queenstown supermarket site returned a negative result.

All 308 tests done in the Waikato (Otorohanga, Hamilton, Matamata, Cambridge, and Te Awamutu) were also negative.

All test results to date done in Christchurch are also negative. Testing groups of the public is continuing, now in Auckland.

In contrast in the US One third of participants in Massachusetts study tested positive for antibodies linked to coronavirus

Around a third of participants in a Massachusetts study tested positive for antibodies linked with coronavirus, according to researchers.

The Mass. General study took samples from 200 residents on the street in Chelsea, MA. Participants remained anonymous and provided a drop of blood to researchers, who were able to produce a result in ten minutes with a rapid test.

Sixty-four of the participants tested positive – a “sobering” result, according to Thomas Ambrosino, Chelsea’s city manager.

“We’ve long thought that the reported numbers are vastly under-counting what the actual infection is,” Ambrosino told the Boston Globe. “Those reported numbers are based on positive COVID-19 tests, and we’re all aware that a very, very small percentage of people in Chelsea and everywhere are getting COVID-19 tests.”


Ambrosino called Chelsea the epicenter of the crisis in Massachusetts. Chelsea has the state’s highest rate of confirmed cases, with at least 712 confirmed cases and 39 deaths – an infection rate of around 2 percent.

Even so, that positive rate must be a concern.

The daily rate of new cases in the US has flattened off but is still running at about 30,000, with a total recorded cases of 728,293.

The death rate has more or less flattened to, but is running at over 2,000 deaths per day (yesterday 2,535), with the total 37,154 which is well above any other country, with Italy on 23,227 and Spain 20,043.

There has only been half as much testing or less in the US than Italy, Spain, Germany, Switzerland, Portugal, Austria, Norway, Israel and South Korea.

The testing rate in New Zealand is a bit behind the biggest testers but is still 50% higher than the US.

New Zealand locked down quicker and more comprehensively than most countries (from 22 to 26 March) and so far has benefited from that.

Our daily increase in cases rose steeply to 70 on 26 March and peaked at 89 on both 2 and 5 April, but has dropped off quickly since then (the last three days have been 15, 8 and 13), even though more testing has been done.

Total confirmed and probable cases over time

So for now Covid-19 looks contained here, but there is now debate and big decisions to be made about how soon and home much to relax lockdown restrictions. Government will decide on Monday whether to drop from Level 4 to Level 3 on Thursday or not.

Some are saying things like Data isn’t enough for this decision, and there are doubts whether the New Zealand goal of eliminating the virus from the country can be achieved. Virologist on latest Covid-19 science:

It will be very difficult to eliminate Covid-19 completely from circulation in New Zealand when so many cases are believed to be asymptomatic, a leading UK virologist says.

Dr Chris Smith, consultant clinical virologist at Cambridge University and one of BBC Radio 5 Live’s Naked Scientists, says he’s been talking to lots of virologists and vaccine experts in the last few weeks and they are very sceptical.

“Most people are of the opinion, given how well optimised this new coronavirus is, it has a really high prospect of becoming another circulating coronavirus and causing seasonal infections and cold-like symptoms or in rare cases more severe outbreaks, because by the time that presumably happens the vast majority of us will have become immune to it either because a vaccine has been invented or because we’ve become naturally infected with it.”

But he believes it will take an extended time before a vaccine is ready and in the meantime many countries won’t be able to sustain lockdown measures, and the disease will resurge as a result.

However the random tests so far suggest there may be few asymptomatic undetected cases in New Zealand.

It doesn’t look so good in the US – A New Statistic Reveals Why America’s COVID-19 Numbers Are Flat

According to the Tracking Project’s figures, nearly one in five people who get tested for the coronavirus in the United States is found to have it. In other words, the country has what is called a “test-positivity rate” of nearly 20 percent.

That is “very high,” Jason Andrews, an infectious-disease professor at Stanford, told us. Such a high test-positivity rate almost certainly means that the U.S. is not testing everyone who has been infected with the pathogen, because it implies that doctors are testing only people with a very high probability of having the infection.

…The test-positivity rate, then, is a decent (if unusual) proxy for the severity of an outbreak in an area. And it shows clearly that the U.S. still lags far behind other countries in the course of fighting its outbreak.

Comparing American states to regions in other countries results in the same general pattern. In Lombardy, the hardest hit part of Italy, the positive rate today stands at about 28 percent. That’s comparable to the rate in Connecticut. But New York, so far the hardest hit state in the U.S., has an even higher rate of 41 percent. And in New Jersey, an astounding one in two people tested for the virus are found to have it.

Five other states have a positive rate above 20 percent: Michigan, Georgia, Massachusetts, Illinois, and Colorado.

In New Zealand difficult decisions need to be made about keeping our Covid-19 infection rate right down, but the US is still battling high infection and death rates and appears to have widespread community infection in some areas.


Leave a comment


  1. artcroft

     /  19th April 2020

    The US seems by default to be going for herd immunity. They’ll have to take the deaths that result but might be better off in the long run. I was working through the list of those people I know who are very economically vulnerable following the lock down. There’s lots of pain to come in NZ.

    • Blazer

       /  19th April 2020

      It will be more painful if people do not adopt a simpler way of life.
      Materialism is quite meaningless.
      ‘ “Most men lead lives of quiet desperation and go to the grave with the song still in them.” – Henry David Thoreau

      • artcroft

         /  19th April 2020

        A simpler life? Some of them already lead simple lives; single income, renting, teaching english on a contract to contract basis. Work which requires open borders. But I’ll let them know Blazer said they need to get even more zen and let go of attachment to things like shelter and food.

        • Blazer

           /  19th April 2020

          we cannot eschew Maslow’s Law…but consumerism,want we…can.

          • Alas, consumerism in some form has probably been around almost as long as people have,

            The term ‘conspicuous consumption’ was coined in the c.19.

  2. Alan Wilkinson

     /  19th April 2020

    The first question is what the test tests?

    Is it antibodies? In that case it seems it won’t pick up younger people that have had the virus as their bodies appear to kill the virus by other means.

    Is it the virus fragments themselves? In that case it will only pick up active or very recently active cases.

    So the follow up question is how many tests would you have to do to find asymptomatic cases in NZ if they are randomly dispersed. For example if you can only find active cases there are about 600 known active cases in NZ you would need to do 5M/600 = 8,300 random tests to on average find one unknown case if half the cases were unknown asymptomatic.

    And the final question is how clustered they are. If you don’t test in the right places you still mightn’t find any.

    So it will take a major effort to produce much confidence there is little unknown infection.

    • Patzcuaro

       /  19th April 2020

      I assume that they have been using the standard coronavirus test that has been in use here. I haven’t heard or read anything indicating that there is currently more than one test being used in NZ.
      Testing based around supermarkets seems like a good idea as they are seeing the most foot traffic at present, apart form hospitals. It would also give the supermarket workers a degree of confidence that they are being adequately protect against the virus.

      • Alan Wilkinson

         /  19th April 2020

        That is the RNA test so it will only find active cases.

  3. Duker

     /  19th April 2020

    Those US statistics are junk science
    A sample of 3000 odd people in Silicon Valley ( Santa Clara County with 1.8 mill people, just south of San Francisco) was tested for anti bodies and adjusted numbers were around 20%
    You cant recruit these people on facebook and call them random by adjusting for various demographics ( match a normal statistical population). Word gets around on facebook and you get people are in a possible cluster of those with the virus frantically searching for a free test, yet without symptoms dont qualify for the federally funded ones.[This is what people who the sample test are saying too]
    There is already questions about using RNA anti bodies and false positives that might be picking up the existing human coronaviruses ( mostly connected with common colds).
    The study was was a draft on preprint server which hasnt been peer reviewed and would have major changes by the time its released for specialists, not every day journalists who barely under stand basic numbers

    Iceland has done real random testing( at first every 10th name in phone book) and quite a big sample considering its 365,000 population and their positive rate is under 1%. Not the 20% plus some claim for US

    There are also to get those over 20% of the population infected , it just cant happen in the time available at the low infection rates of Covid 19. Its 1/10 or so that of measles one the racehorses of infection spread

    • Alan Wilkinson

       /  19th April 2020

      The NY study was antibodies. I think the Iceland test was RNA. They are not comparable. Neither have been the known infection rates in the two areas.

  4. David

     /  19th April 2020

    There is so much confusion about this damn virus with these tests showing anything from 1 to 50%, the antibody tests having a very high false positive rates.
    The vaccine debate is the same with people saying 18 months if we are lucky with Oxford university saying september, Johnson and Johnson saying the end of the year and building manufacturing capacity ahead of that. 70 vaccines are being trialled with 4 now in humans.
    The Trump touted Hydroxychloroquine and Remdesivir are being discounted, especially the former, by vast swathes of the media yet there are huge trials of it globally including here in NZ.
    Ventilators have gone from must need to potentially worsening the symptoms, hospitals supposingly being overwhelmed to being half empty.
    The death rate in the UK has spiked but there are concerns its heart attacks, cancers and other ailments people are too scared to go to the hospital about as much as its Covid.
    And the big question is all these locked down countries have to re open and are we to see a second wave bigger than the first but we just have to live with it as a seasonal problem or will it go like other outbreaks and just mutate into something less deadly.
    If the world gets to just live with it what are the implications for NZ.

    • artcroft

       /  19th April 2020

      “The Trump touted Hydroxychloroquine and Remdesivir are being discounted,”

      Don’t forget the Trump touted wall that many said he’d never build, that he never built.

      Don’t forget Trump touted himself as a great military leader verse the stupid generals who didn’t realise that you can sneak hundreds of tanks, trucks, artillery pieces across the Syrian desert at night to surprise attack ISIS in the morning, because you can’t do that.

      So when Trump touts something the media is just pointing out he doesn’t know what he is talking about.

      • duperez

         /  19th April 2020

        Which wall was that? The one that’s been in the news in the past two days?

        “The US Army Corps of Engineers has reportedly doled out over a half a billion dollars to a federal contracting firm to build sections of Trump’s border wall at an above-market rate.
        The Daily Beast reported on Thursday night that the Army announced a $US569 million no-bid contract to BFBC, a firm affiliated with Barnard Construction, to build 17.7 miles of the border wall.”

        • artcroft

           /  19th April 2020

          Wow 17.7 miles of wall, at an above market rate. Can’t have much more than 1000 miles to go I guess.

          • Really ? Now that IS progress. In round figures, because I can’t be bothered to do it exactly, that’s about $3,000,000 a mile; what a bargain.

  5. duperez

     /  19th April 2020

    Big differences? There’s more than a slight difference between the press conferences with the leaders of the two countries in their (almost) daily updates.

    The rambling from Trump in today’s session would be been as bizarre in most countries in the world. It’s their ‘normal.’

    Early parts today bought Olympic equestrian events and myself to mind. A New Zealander has posted their score and when rivals from other countries are doing their circuits I’m yelling at them to kick rails down or fall off. There was a touch of that this morning, Trump gleeful about other countries having more deaths per capita than the USA.

    On April 1st when he didn’t want to talk about US deaths there were 4,000. Today there are 39,000.

    But he’s onto it, including China putting out false numbers. The truthmeister!


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: