Contact-tracing will be the Achilles heel of the COVID-19 program at LEVEL 3

There are big risks to the COVID-19 campaign if we move to LEVEL 3 too quickly without greatly improved contact-tracing. There is no way back if we get this wrong

Last Thursday (9 April), many Kiwis would have been feeling very proud of themselves with only 29 new cases of COVID-19, both confirmed and probable, announced that day. It looked like we were smashing COVID-19.

By Friday 10 April that did not seem quite so clear cut, with new cases up to 44. Suddenly, the chances of going to Level 3 on 22 April following the planned Cabinet Meeting on 20 April started to look more wobbly.

Two days later on Sunday 12 April, we are down 18 new cases. Things are looking much better again, albeit off lower testing numbers.

The big question right now is whether, given this combination of trend and volatility, we can be ready to go to Level 3 by 22 April. That could mean most people then getting back to work, but combined with social distancing and no mass events.

Stamping out becomes much harder at Level 3

If our New Zealand policy really is to stamp out COVID-19 and not just to suppress it, then the Achilles heel of the Level 3 policy will be any failure to hunt down every single case of community transmission. This community transmission was the key reason we had to go to Level 4 lockdown in the first place.

The statistic that stares us in the face right now is the that we currently have two percent of cases of confirmed community transmission (approximately 26 people) combined with the 11 percent of current cases (>140 cases) whose origin is unknown. Many if not most of these cases of ‘unknown’ origin are likely to be community transmission.

The fact this ‘unknown’ number is so high tells us very clearly that the current contact-tracing program is overwhelmed. It also means that the process of working through the contact-tracing for each unknown case is taking many days, and that is not good enough for Level 3.

Our health authorities have been consistently reluctant to acknowledge any weaknesses in their program, be that at overall Ministry level or at District Health Board level. Their denials fly in the face of reality. In the long run, it is always better to be transparent, but it is something that Ministries struggle with.

Part of our current problems may well be linked to the regional system of health delivery in New Zealand. Each district does things its own way, with the Ministry focusing on policy but not delivery. The current situation with clusters and associated tracing, with most of the clusters spread across the country, illustrates that point.

In the case of the Bluff cluster, it is apparent that not one person actually lives in Bluff and the cluster members are wedding attendees from all over the country. Consequently, there is a lot of information sharing between Health Boards that is needed. If each Health Board is only seeing its own data, then information integration and co-ordination become big issues. In normal times, there is much to be said for decentralised decision making, but in a time of war co-ordination is paramount.

As long as we remain in Level 4, then the currently inadequate tracing is not fatal to the program. This is because formation of new clusters is heavily constrained, given that people are in most cases remaining in their bubbles.

Under Level 3, that changes, with much greater possibility of community transmission that seeds new clusters which then fan out across the country and feed on each other. This is the disaster that we should all fear.

Without antibody testing combined with back-tracing the risks are much higher

The evidence from Iceland now seems clear that up to half the people infected with COVID-19 may have minimal symptoms. However, in a track and trace campaign we still have to find these people as they are part of the transmission pathways. Without a combination of antibody testing plus PCR (swab testing) working in combination, the program is unlikely to succeed. Our Government has yet to commit to an antibody-testing program.

The key reason that most other countries including Australia are focusing on suppression rather than elimination is that they doubt whether they can stop all community transmission. In large part, this is because they doubt that they can maintain an ongoing ‘social licence’ for a Level 4 type of lockdown. In this context, China and New Zealand are the only two countries that appear to have been explicit that their aim is total elimination.

Given this situation, then we have to put a lot more work into contact-tracing and getting those systems set-up with appropriately trained staff. It is no good just being as good as other countries. We have to be better, given that our policy, is to ‘stamp it out’ and not just suppress.

One of the good things that New Zealand can expect in coming days is that the number of people with ordinary flu who come in for testing should start to decline very quickly. This is because the Level 4 system that we currently have in place should be smashing any community transmission of ordinary flu. This will ease up some resources that can be allocated to testing all close contacts.

Some weeks ago, Kiwis could take comfort that New Zealand was doing better than Australia. Our overall levels of infection were much lower, even on a per capita basis. However, that is no longer evident. Per capita total infection rates are now similar in both countries. More importantly, Australia’s per capita rates of new cases are now less than half of ours, having previously been well above us. What are they suddenly doing better than us to achieve this?

There is no clear-cut answer to this, but it is apparent that Australia’s testing of people with symptoms got up to speed more quickly than in New Zealand, all within well-oiled state health systems. In contrast, New Zealand got off to a very slow start with very low testing capacity, with that reality never acknowledged by the authorities. Ironically, Australia may yet spoil its advantage by now taking the brakes off too soon.

Rigorous back-tracing is a daunting task

The way a top-quality contact-tracing and testing program needs to work is that results of testing must be available within hours of the testing taking place. It needs to be same day testing, with couriers travelling hourly between testing centres and the laboratories.

There must be results for every person who is tested within a matter of hours. If that means laboratories working at night, then so be it. This is a war.

At the same time that an infected person or suspected infected person goes into isolation, the contact tracers needs to swing into action. It can’t be the next day; it has to be the same day.

All close contacts must be identified going back some two weeks.

The most recent contacts are the easiest ones. These are the forward traces. These people all have to go into immediate self-isolation. Ideally, they should also then be tested every day. This is probably best with the existing PCR test, but possibly in conjunction with serology (antibody testing).

Identifying close contacts for the prior 14 days will be very challenging for most people, especially once we come out of our bubbles and are moving around more under Level 3. Accordingly, we should all be asked to keep a diary of our close contacts to allow this back-tracing to occur. No ifs or buts; this has to happen.

Whereas forward tracing is to identify people that might be in the incubation stage, back-tracing is to identify earlier contacts who may have been the source. There is little point in testing these back-traces with the PCR test because if these people have recovered then the result will be negative. But a serology test for antibodies will identify the possible source. Having narrowed down the suspects in this way, a PCR (swab) test can then be used to confirm if the person is still infected. As a matter of risk minimisation, and given the false negatives that occur with PCR testing, that person should still go into self-isolation for at least a week.

Many of these back-trace people are themselves unlikely to be infectious, but their own forward-traces will probably still be infected. And so we need to go forward again from there, to find those new forward-traces to catch these people who may well by then be seeding their own clusters.

There is also a current weakness in that we are assuming people have stopped shedding the virus if testing is negative for two days following cessation of symptoms. That criterion is possibly OK for countries that are only trying to suppress, and it seems that it does align with WHO advice. But if we want to stamp out this disease then we have to be tougher. One week of negative test results after cessation of symptoms would be safer.

Now, some people are going to say that this all sounds very daunting. Well, rigorous contract-tracing and quarantine is daunting. But if we want to stamp out this disease then either we have to stay in Level 4 for many more weeks and possibly months, or we need to set up a comprehensive track and trace.

There are two parts to making it work. One is that the Ministry of Health and the Health Boards need to get themselves much better organised for the track and trace. The other part is that every one of us needs to start keeping those diaries. I say again, no ‘ifs and buts’, absolutely everyone. We are all in this together.

Our Government hopes to use an app from Singapore to help identify where infected people have travelled and who they have come in contact with. But the app won’t be ready until some time in May. It is therefore no substitute for diaries that we can be keeping as of now. My broader family, which includes multiple bubbles and a health worker, is already doing this.

As long as we are in Level 4 we can win the war, but we can’t stay there for ever.

The overall trend of the last few days tells us with reasonable clarity that we have dropped the transmission rate, R, well below the critical level of ‘1’. That means we can have an expectation that as long as we stay in Level 4, then numbers will further decrease, but with ongoing volatility. If only we could stay in Level 4, then eventually the disease would die out.

To reduce volatility when analysing the data, I use three-day rolling averages. Our latest three-day average of new cases is 30 (comprising 44, 29, and 18 cases). A week ago it was 81. If we can keep driving it down at about that same rate of 63% decline in a week, then we will be down to a three-day rolling average of about 11 cases by the time Cabinet meets on 20 April.

If we can get the daily new cases to somewhere around 10 to 12 people by that time, then in theory we should be able to pour lots of resources into identifying the forward and back traces for each of them.

In working out more precisely where we stand, we need information each day as to how many of the new cases involve transmission ‘within bubble’, how many are from ‘outside bubble’, and how many are from within Government-managed isolation. All of this information must surely be known for each case from the outset.

In contrast, it is no longer particularly relevant to current decision-making as to how many historical cases came from overseas travel, and how many are close contacts. We need to know what is the situation with the latest cases.

If there are still any cases coming through the system from ‘outside bubble’ then something is going wrong given that we have been in our bubbles for more than two weeks.

Is 22 April too soon for Level 3?

Given all of the current uncertainties, my own inclination is that April 22 may well be too soon to come out of Level 4. My preference would be to stay in Level 4 for another 2 weeks and then move very fast down through the levels from there. But it does all depend on getting the track and trace system operating at a much higher level than currently.

I believe New Zealanders would accept anther two weeks of Level 4, if that then allows us to move much more quickly down through the other levels.

Once we do move to Level 3, then we must place all close contacts of existing cases under very tight isolation, as if those individuals are still in full Level 4. Otherwise, Level 3 is doomed to be a failure. That failure is essentially what has happened in some of the East Asian countries like Japan and Singapore where they are now moving from soft isolation policies to harder policies.

As a person who comes from animal-based industries, I have been in many discussions with Ministry of Primary Industries (MPI) over the last three years about some remarkably similar issues that have had to be addressed with the Mycoplasma bovis campaign. That Mycoplasma bovis campaign is still ongoing. Failures to undertake track and trace with sufficient speed and rigour, together with an unwillingness of MPI during the first 21 months of that program to acknowledge problems that were evident to all of us in the field, lie at the heart of the problems that campaign has faced. Even now, we still don’t know whether it is the Mycoplasma bovis authorities or the disease that is running the fastest. That race is still ongoing.

Somewhat ironically, it is animal scientists around the world who have the most experience in running disease eradication campaigns, be that TB, bovine leucosis, brucellosis and now Mycoplasma bovis here in New Zealand, or internationally for foot and mouth and mad-cow disease. In contrast, the human epidemiologists have never had to wage an eradication campaign except in situations where they have had a vaccine to create immunity and thereby carry the burden of the campaign.

One of the lessons from the animal world, is that every disease has its unique characteristics that determine the specific strategy. But every time, one way or another, it requires a track and trace that is carried out with speed and rigour.


About Keith Woodford

Keith Woodford is an independent consultant, based in New Zealand, who works internationally on agri-food systems and rural development projects. He holds honorary positions as Professor of Agri-Food Systems at Lincoln University, New Zealand, and as Senior Research Fellow at the Contemporary China Research Centre at Victoria University, Wellington.
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18 Responses to Contact-tracing will be the Achilles heel of the COVID-19 program at LEVEL 3

  1. granthod says:

    Thanks Keith, very informative.

  2. Matthew R Grierson says:

    Yeah, great suggestions, but I can’t see the government listening to these suggestions any more than they have with Mycoplasma. Plus people are impatient and often ignorant. Pushing the lockdown out another two weeks, even with testing and tracing set up will be a big ask and hard sell.

  3. Greg van Paassen says:

    I’m listening to a podcast that describes several alternative plans (The Weeds on Vox, “How does this end?”; focussed on the USA of course).

    It seems clear that a combination of strong border controls, location tracking, China style temperature checks, mass sample testing (at least for essential workers), contact tracing, control of mass gatherings (sports games, concerts, etc.) and support for households is the only feasible way forward.

    At least until an effective vaccine appears (or 2030, whichever comes first).

    An informal poll by The Spinoff (or reported by it, at least) suggests most people are OK with location tracking by government agencies in NZ. We have a very high level of trust in our government, a level that other countries can only dream of.

    So we can’t go back to normal, but I think we can go forwards to normal – the new normal.

  4. Tania says:

    Hi Keith, I am really struggling to understand how we could justify and economically afford to stay at Level 4 any longer than the 4 weeks, given that it has become increasingly evident in NZ that Covid-19 causes a tiny amount of deaths or even hospitalisations. Our hospitals have probably never been so empty, yet we have completely stalled our economy, the consequences of which are yet to become fully apparent. We can only imagine right now. I really do think that the cure is going to be far worse than the disease for many countries such as NZ and Australia where the death and hospitalisation rates are very low, and I speak as a former registered nurse. Given that we know that up to 80% of the population can be infected with Covid-19 and be totally asymptomatic, or have very mild symptoms, I am finding it very difficult to see why we need to be on the path of eradicating Covid-19 entirely. It just doesn’t make any sense to me

  5. Tania says:

    Hi Keith, I am struggling with how we could justify the need to extend our Level 4 lockdown beyond the current four week period. It is now becoming clear that in NZ the death rate and even hospitalisation rate from Covid-19 is extremely low. Our hospitals are probably the emptiest they have ever been, as the influx of Covid patients has never arrived. I am very much suspecting that the cure is going to be far worse than the disease in countries such as NZ and Australia, where in reality the virus does not cause severe illness in the vast majority of cases, yet our economies have been stalled almost completely. We can only imagine the consequences of this in the days, weeks, months and years ahead. We know from evidence in Italy now that up to 80% of those infected with Covid-19 are asymptomatic or have very mild symptoms, yet NZ still sees the need to eradicate the virus, which means that our borders cannot be reopened without a mandatory 2 week quarantine until the virus is eliminated globally or there is a vaccine, both of which are probably over a year away. In the meantime almost all of those businesses dependent on overseas tourists lose their livelihoods. I write all of this as a former registered nurse who worked in public hospitals for years, and I have been pondering all of this for a week or so now!

  6. Tania says:

    Sorry, did not mean to post twice! I am a novice at posting and thought I had deleted the first one, sorry about that!!

    • Keith Woodford says:

      No need to apologise. I have been known to double post myself. Also, as a first-time poster to my site, your first post would have been sitting in the queue to be approved, and once I approved that, the second post was then automatically approved.
      I think that the overseas tourist industry was going to be destroyed regardless of anything we did, as tourists would not be able to get back to their own countries without extensive quarantine. Also, demand for some of our exports would still have been affected, and our import supply chains would also still be disrupted by events in other countries. And we would still have had to try and flatten the curve to stop the health system being overwhelmed.

  7. Tania says:

    Thanks Keith, and yes I see your point regarding tourism, but if NZ are going for eradication of Covid-19 then surely we will be one of the very last countries to reopen our borders?
    But more I am struggling to see how NZ can consider extending the Level 4 lockdown, or even an extended period at Level 3 when the numbers of those hospitalised and dying from the virus are so low here. Surely it is economic suicide for so many businesses to be closed and with zero income, when it appears to me that the virus can be managed rather than eliminated without putting undue strain on our health system. I was fully supportive of the full lockdown for the first couple of weeks, until it became apparent that it wasn’t going to be the public health disaster we are seeing elsewhere, now I just can’t see the justification for it……

    • Keith Woodford says:

      I think the key point is that cases and hence deaths are only so low because we are in Level 4. I expect deaths will go up in the next couple of weeks as death rate typically reflects new case numbers from about two weeks or even three weeks earlier. Yes, they will still be low, but if it were not for Level 4 then we would be on the same trajectory as, for example, the UK.

  8. Kate Moriarty says:

    Your statement thar “ cases and hence deaths are only so low BECAUSE we are in Level 4” should be on newspaper headlines everywhere as a reminder.

  9. David Porter says:

    The real problem for the Cabinet on the 20th is that if they enforce lockdown for another period of time, the public loses patience as there are few deaths and hospitals are not overwhelmed causing people to think everything is ok so why lock us down. If they go to Level 3 without the ability to contact trace and cases/deaths spiral, they will be accused (rightly) of contributing to the problem.
    Who’d be a politician eh?!

    • Keith Woodford says:

      Yes, I agree about wanting or not wanting to be a politician. But there is always someone wanting to step up. And sometimes adversity does bring forth a real leader.
      The media keeps talkng of ‘experts’, but it is a flawed idea; all of us are learners trying to make sense of the data.
      The last few days have been particularly difficult with the ‘Easter effect’ across most of the world influencing recorded data. Today and tomorrow are the catch-up days in that regard.
      My own judgement is that here in NZ, the population is still solidly supportive of our Prime Minister, including a huge band of supporters following her on facebook where she updates morning and night.
      It seems that the only country still hoping for herd immunity is Sweden, and as we come out of the ‘Easter effect’ their numbers are of increasing concern. Who would want to be their State Epidemiologist! Under their remarkable constitution he is the person with the decision making power. Despite hs public stance, he must be incredibly nervous.

  10. Brian Dingwall says:

    Hi Keith,
    Thank you for the work you are doing. Not many experts combine the science and the business (or economic) expertise that you do.

    I’m afraid my diary would consist solely of imprecations caused by various randoms (dog walkers, walkers, cyclists, and worst of all, runners widely exuding various respiratory effluviations) getting too close on walking trails…not especially useful I would have thought.

    One idea…..where are the dairymaids, is anyone looking for them? Jenner’s insight was that previous infection with one species of variola virus (cowpox) provided some degree of immunity to another (smallpox). Is it possible that collectively we are not all totally immunologically naive to the some of the antigenic material on the coronavirus, since many of us have been infected with one or more colds caused by viruses of the same genus (of which I understand there are at least four). I have seen various assertions that we are all naive wrt the “novel virus” but no evidence thereof. This may explain why in so-called “petri dish” situations e.g. on cruise ships not everyone gets infected, and many are asymptomatic implying I guess that their immune systems are recognizing the invader and dealing promptly with it. The key here is for researchers to be looking at those we would reasonably expect to be infected but aren’t, rather than only at the infected population and the virus itself. Any thoughts?

    • Keith Woodford says:

      Thanks Brian
      The virus is actually very similar to the SARs virus from 2003 or thereabouts.
      I saw Peter Doherty say that it was a pity that the work on a SARs vaccine, which was very promising, did not contnue. That was something he would know something about.
      I think there has to be a reasonable chance that a somewhat generic coronavirus vacccine woul give some protection, at least for a reasonable time.

  11. Gideon says:

    The harsh reality in eradicating Covid-19 is that life has to continue… for ‘the sake of the economy’, albeit never ‘normal’ again.
    With the infection rate which could be FIFTY times higher than portrayed in the media, this virus is highly infectious but the mortality rate (although it doesn’t seem so), is not so high if you take the asymptomatic cases (I would call them ‘spreaders’) into consideration.
    In all, total eradication would just not be a reality and would take up considerable resources from the government to ‘keep on fighting.’

    Although the flu is not nearly as infectious as Covid-19, no government has ever ‘eradicated’ this virus… or never felt the need to since it just isn’t ‘that deadly’? So we just need to carry on (as ‘worker bees’); pay our taxes to keep the koffers of the government at an optimum level. This is the overwhelming resonance of governments across the world – TO ‘OPEN’…

    • Keith Woodford says:

      The NZ testing data, although not adequate to demonstrate that we do not have COVID-19 circualating at low levels in the community, is now sufficient to demonstrate that the level circulating in the community is very low.
      The reports as to high levels of the virus circulating in the community are based on a msinuderstanding as to how antibody tests should be interpreted. Antibody tests are unlikely to have a specificity of more than about 98%. Hence, when the clincal cases are very low, such as in NZ where it is at a prevalence level of 0.03%, then it is easy to get antibody tests giving false positives at more than fifty time the true prevalence level.
      Antibody tests can be very useful, for example as a filtering mechanism in the search for true positives, but can lelad to false conclusions if used in the wrong way or in isolation. They are just one weapon in the armoury.
      I may write an article on this when I get some time.

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