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.

*Keith Woodford was Professor of Farm Management and Agribusiness at Lincoln University for 15 years through to 2015. He is now Principal Consultant at AgriFood Systems Ltd. . He can be contacted at kbwoodford@gmail.com. Keith’s previous COVID-19 articles are available here.