Category: Our Posts
Summary
New Zealand is facing a serious threat to the nation’s health from COVID-19. Thus far, the health system has coped well. We currently have over 1300 cases with little evidence of strain or excess premature death.
The government and its advisors have articulated a strategy of ongoing lockdowns of New Zealand society for the foreseeable future in an attempt to eradicate the virus. We believe that holding out for vaccine development or pursuing an aggressive eradication policy are not realistic.
We are a group of academics who are concerned that such a strategy is not proportional to the threat posed by COVID-19 to New Zealanders’ health and that it is likely to substantially harm the nation’s long-term health and well-being, social fabric, economy, and education.
We recognise that COVID-19 has overwhelmed some hospitals overseas, with overflowing intensive care units in some densely populated cities, such as New York, and Milan. This is the principal risk posed by the transmission of the virus and we seek to avoid such a situation in New Zealand. In some European countries, there is excess mortality attributable to these outbreaks. Rest homes are especially vulnerable to outbreaks caused by the virus.
We believe that such a scenario is less likely to occur in New Zealand due to our lower population density. We also see that Australia, a country with greater population density in some regions, but in many respects, similar to ours, has seen sharply reducing disease incidence for several weeks, despite having a more relaxed lockdown policy.
We believe that it is in the best interests of the country to rapidly transition to a situation similar to the government’s alert level 2, while closely monitoring the spread of the virus and its impact on the health system. This would enable the majority of businesses to continue to operate and schools and universities to open. It would also allow essential domestic travel to resume.
We believe that an exclusive focus on the number of new cases of COVID-19 is less important than measures of whether or not the spread of the virus is causing an increase from background rates of hospital admissions, premature deaths, and intensive care bed occupancy. These latter measures are more important than the former in terms of deciding whether or not the country should be placed under strict lockdown in the future.
A focus of our response to the virus must incorporate returning to normality as soon as possible.The likely course of the virus is that many individuals will be infected with the virus and immunity in the population will develop. We understand that laboratory services are currently stretched by focus on PCR tests for the virus. However, we believe serosurveys of immunity would provide valuable information about the extent that the community has been exposed to the virus.
Up until now, the government has been selective in the information it is choosing to share with New Zealanders. We do not have a clear picture of what the government’s response will be in the next nine months and have had to guess this from comments of its advisors. We have not been told that spare capacity at Auckland hospitals is currently high, for example. We believe that New Zealanders should be free to debate the direction that the country will take in the next nine months, and that transparency should be a guiding principle for leading the country through this crisis.
What is COVID-19 and SARS-CoV-2?
SARS-CoV-2 belongs to a large group of viruses called “coronaviruses” that cause diseases in animals and humans. The first case of pneumonia associated with the virus was reported from Wuhan city, China, on the 12th of December 2019, and the outbreak was reported to the World Health Organisation on the 31st of December 2019. Cases had a shared history of exposure to Huanan seafood markets, indicating a likely animal source.
Six types of coronaviruses are known to affect humans. Four cause common cold type symptoms and two others cause severe illness: middle east respiratory syndrome (MERS) and severe acute respiratory syndrome (SARS). The clinical syndrome associated with this virus is called COVID-19, and is characterised by cough, muscle aches and shortness of breath. Hospitalised patients develop pneumonia or lung infection. The diagnosis is made by a genetic test for the virus (PCR) from a swab taken from the back of the nose. Some patients who develop the pneumonia require mechanical ventilation in intensive care units. Conversely, about 50% of people who test positive for the virus have no symptoms in community surveys of the disease carried out in Iceland.
Now, more than 1.2 million test positive cases have occurred worldwide. The first case occurred in New Zealand on the 28th February 2020. At the time of writing (Sunday 12th April 2020), New Zealand had a total of 1,330 cases, with 14 currently in hospital, five in intensive care and four deaths. Deaths so far have occurred in people aged in their seventies to nineties with comorbidities. We do not have sufficient details to assess, but it is likely that some of these deaths were with the virus rather than a direct result of infection.
The rapid spread of COVID-19 has posed a risk to the health of populations. For example, intensive care units in several countries (for example: Italy, Spain and New York) were overwhelmed with a sharp rise in the number of cases which require mechanical ventilation, such that hospital facilities and personnel are substantially stretched. This increases the risk of transmission of the virus to other elderly patients and to staff.
What has New Zealand done to contain the virus in the short term?
New Zealand has introduced wide ranging and tough border restrictions on international visitors. Large gatherings were progressively banned. On March 25th New Zealand went into “lockdown”, including the closure of schools and non-essential businesses. Since the lockdown, new case numbers per day have stabilised and recently started to decline.
What is the government’s long-term plan?
The government has not clearly articulated a long term plan to address the threat. Government advisors have articulated such strategies such as waiting for the development of a vaccine and elimination of the virus, which would entail prolonged lockdowns.
Why are we challenging the New Zealand Government’s response?
The risks of the virus have been overstated
It is clear now that much of the modelling related to the mortality associated with COVID-19 was overestimated, including for New Zealand. In early March, the World Health Organization reported a Case Fatality Rate (the proportion of deaths that occur in individuals who are test-positive for SARS-CoV-2) of 3.4%, but this crude measure ignores undetected infections in people with no symptoms and therefore likely overstates the true CFR. New Zealand’s own modelling in late March predicted that 80,000 kiwis would die without mitigation measures (a CFR 1.6%) and based on the assumption that all New Zealanders would be infected – a highly unlikely scenario.
But now, with time, the picture is becoming clearer. With over 1300 confirmed and probable cases and four deaths, the overall CFR in New Zealand is approximately 0.30%. No deaths have yet occurred in people under the age of seventy. This overall CFR rate is similar to that seen for seasonal flu epidemics and indicates that the virus poses a low risk of fatality to the vast majority of people. As Dr Jay Bhattachayra (Professor of Medicine at Stanford University, USA) points out – the response, and the policies and strategies to stop the spread of an epidemic virus strain must be commensurate with the threat posed by the disease.
Since the average age of COVID-19 deaths has been in people aged 80 years, a large majority of cases have occurred from their comorbidities rather than from the virus alone – as is the case with all New Zealand’s deaths to date. An analysis by Professor David Spiegelhalter at Cambridge University shows that the CFR from the disease is conservatively estimated to be about the same as an individual’s average annual fatality rate. In effect, it is like squeezing a year’s mortality risk into two weeks. In Italy, a review found that just 12% of reported COVID-19 deaths were likely to be directly due to the disease. As Stanford epidemiologist Professor John Ioannides remarks of COVID-19: “it is only this year that every single case and every single death gets red alert broadcasting in the news.” In the past, such deaths would have not been attributed to a single virus, since extensive testing for these viruses had not been carried out.
The majority of severe outbreaks of COVID-19 globally have occurred in regions with very high population density, including London, Milan, New York, Wuhan and Madrid. Auckland, in contrast, has at least one third lower population density than the least populated of these cities. Population density is likely to be an important factor in the transmission of the virus, resulting in overwhelming limited health facilities.
Eradication of the virus while desirable is highly unrealistic
While laudable, the focus of the government has been on eradication of the virus. We believe this to be unrealistic. To date, no country has successfully eradicated a virus like COVID-19 that causes a high proportion of asymptomatic infection. The usual course during an epidemic is for susceptible individuals to get infected and develop immunity so that eventually the virus has nowhere to go. We agree with the widespread approach of ‘flattening the curve’ which seeks to reduce rapid spread so that cases can be accommodated by the health system.
The diagnostic test (PCR) used to identify cases is not sensitive. This is demonstrated by the growing number of test-negative positive cases with compatible symptoms who have had contact with positive cases. This means that the test is not ideal, and it will, therefore, be almost impossible to tell for certain whether the virus has been eradicated.
Complicating the eradication strategy is that the virus is likely to be more widely dispersed in the community than has been appreciated. For example, community studies from Iceland show that the population has high levels of asymptomatic test-positive cases. Half of the test-positive cases are asymptomatic. Such a study has not been done in New Zealand. Instead, allowing the population to develop immunity, which is a natural defense for the virus after infection could occur, and manage the spread of the virus while protecting those most vulnerable from the disease.
A German study in the town of Gangelt showed that about 2% of the population tested positive by PCR, indicating current viral infection. One in seven subjects (14%) had evidence of immunity to the virus, indicating that they will have low risk of re-infection. This means that in many countries, the virus has spread much further than is indicated by tracking new cases of PCR test-positive people. Until such a study is carried out in New Zealand, we can not determine this.
New Zealand cannot “hunker-in-a-bunker” until there’s a vaccine for a virus that is likely to become endemic in the rest of the world. Tourism, for example, is one of our most important industries, with annual tourism expenditure in New Zealand of $40.9 billion – that’s $112 million per day. Under an elimination scenario – we would lose our entire tourism sector as it is highly unlikely any tourists would incorporate a 2-week quarantine period into the start of their NZ holiday schedule. We cannot shut ourselves off from the world as we attempt to eliminate the virus and await the hopeful arrival of a vaccine that may take several years.
Managing risk to the health system
One of the risks of COVID-19 to a nation is the potential to overwhelm a healthcare system, particularly with respect to capacity to treat patients who require mechanical ventilation. New Zealand currently has 153 dedicated intensive care beds. However, in a crisis, the Ministry has indicated that up to 520 ventilators are available. In New Zealand only a small percentage of cases have required hospital treatment and even fewer require intensive care after a thousand test-positive cases. Hospitals are now at ~50% of their total capacity. Clearly, up to now, the virus has not had the devastating effect on hospital services as it was thought to. A managed spread would lower the rate of spread to levels that do not overwhelm health services.
A prolonged lockdown – the social and economic effects
This is the first ‘lockdown’ in New Zealand’s history. Small businesses are particularly vulnerable, especially those reliant on overseas visitors. We are already seeing a spike in unemployment claims and business insolvencies. The human cost of job losses and bankruptcies will be massive. In Spain, after a prolonged lockdown, unemployment percentages are now doubling every week while in the USA new jobless claims have exceeded 16 million. The impact on the global economy will likely be as heavy as the great depression.
Civil liberties in New Zealand are now eroded with unchecked State of Emergency powers. Confidence in the police is undermined. With the single focus of the health sector on COVID-19, important other treatment is being forgone, such as cancer surgery.
A prolonged lock-down and subsequent economic decline will also have numerous other implications like increased poverty, mental health problems and deaths. During the lockdown families will be unable to celebrate births and support their new family. Husbands, wives, sons daughters and other fr will be unable to comfort or say goodbye to some of the approximately 2,700 people who will have died in New Zealand due to natural causes over the four week lock-down period. This was detailed by Dr Elana Curtis (Te Arawa) from a Māori perspective. It will even impact our Predator Free 2050 ambitions and harm our native Taonga like kiwi. The evidence for the most aggressive lock-down measures is lacking and much of the pain of this shut-down will be borne by the socio-economically disadvantaged and our younger members of society.
Lastly, there is a real risk of damaging our ability to manage future pandemics – “over-reaction may damage the reputation of science, public health, media, and policy makers. It may foster disbelief that will jeopardize the prospects of an appropriately strong response if and when a more major pandemic strikes in the future.”
What should New Zealand do in the next nine months?
Cases are now in decline. We understand the decision to lockdown given the lack of data. But, it is now clear that COVID-19 affects different people and populations differently. We believe that the risk posed by the virus to the vast majority of the population does not justify ongoing lockdowns, which entail serious social, educational and economic consequences. We should, therefore, plan for coming out of lockdown by defining and stratifying risk groups.
New Zealand has enacted an efficient system for case identification and quarantine to contain the risk of further spread after imported cases were initially detected from overseas. Hospitals have also gone to great lengths to prepare for new cases.
Where our opinion differs from current policy is that we should now prepare to come out of lockdown and move to a situation similar to alert level 2 at the end of the four week lockdown period. Evidence from Australia indicates this is safe to do. Despite far less stringent lockdown rules, their new infection rates have been sharply declining for the last three weeks. This is also in Australian cities which have a higher population density than Auckland, such as Melbourne and Sydney. This would allow most businesses to open, and allow schools and Universities to reopen. Domestic travel should also be opened. South Korea and Singapore have followed such a strategy.
At a community level, we seek to avoid a situation in which clinical and public health response to the virus is overwhelmed. We believe that hospitals should be monitored for overcrowding and limited capacity in intensive care. At the time of writing, Auckland hospitals are at half capacity and not overwhelmed. This is the principal factor which should guide intensification of social distancing measures. Similarly, adequate capacity should be afforded to include adequate contact tracing and quarantine of newly identified cases.
We believe that testing of populations for serological evidence of immunity would help us better understand the threat posed by the virus. We understand that laboratory resources are currently stretched. However, such a study would give crucial information about exposure to the virus that would be useful for guiding further policy to contain the risks posed. This would be especially important for people who are at raised risk of fatality from the virus.
We agree that mass gatherings (>100 people) should be cancelled. Isolation of rest homes is especially important. People who are at high risk of severe complications of the disease, by virtue of age and sickness remain at home, with state funded support provided to maintain such people in good health. Given the high rate of imported cases, we agree that entry border measures remain maximised.
We believe that an exclusive focus on the number of new cases of COVID-19 is less important than measures of whether or not the spread of the virus is causing an increase from background rates of hospital admissions, premature deaths, and intensive care bed occupancy. These latter measures are more important than the former in terms of deciding whether or not the country should be placed under strict lockdown in the future.
We believe the government should be open about how it is making far reaching decisions about New Zealand’s future. We have seen some information shared, however, much is kept secret. We have not been clearly told what the government’s future strategy to address the pandemic is. With such high stakes, we believe the government needs to be transparent about sharing its decision making with its constituents.
Our 10 point plan
- Low risk people should be allowed to return to their normal daily activities. For example:
- Schools and universities should reopen.
- All leisure activities are permitted
- People should be allowed to return to work. Those over 60 and or with underlying health conditions, and those uncomfortable returning to work, could continue to work at home with support from their employer and government.
- Domestic travel by any means is allowed.
- People at high risk of severe complications by virtue of age (> 60 years) or medical conditions (such as diabetes, cardiovascular disease, cancer or are immunocompromised) should continue to self-isolate and maintain social distance. These people should receive state-funded support and priority care. For example, supermarkets should prioritise all such people for at-home delivery.
- Health professionals should carry out strict hand hygiene and be provided all necessary personal protective equipment.
- High risk communities and groups, with particular focus on rest homes, should be protected from COVID-19 cases or infection and provided government support to do so.
- Gatherings of over 100 people are prevented.
- Encourage improved hand hygiene and exclusion policies for ill workers.
- Border entry is restricted for the near-future to reduce the risk of imported infection.
- Monitor hospitals for overcrowding and limited capacity in intensive care.
- Contact tracing and quarantine of newly identified cases is essential. Resources should be made available to ensure this is adequately carried out.
- Seroprevalence surveys, with PCR, should be considered to assess the proportion of the population who have been exposed to the virus. This would give valuable information about further risks posed to high risk individuals to facilitate their return to the community.
There is a trade-off: how many lives will be taken by Covid-19 and how many lives will be lost due to our attempts to prevent loss of lives from Covid-19, writes Professor Ananish Chaudhuri of the University of Auckland
In his book “Risk Savvy”, the behavioural scientist Gerg Gigerenzer notes that, in the immediate aftermath of September 11, 2001, many Americans decided that flying was too risky. Instead, they chose to drive. In the 12 months following the attacks, an additional 1,500 people lost their lives on the road while trying to avoid the risk of flying. This is more than the total number of passengers in the planes used in the attack.
A similar phenomenon is playing out right now as the world essentially comes to a standstill to prevent deaths from Covid-19. But in doing so, we are focusing on what the psychologist Daniel Kahneman calls “identified lives”; the loss of lives that are right in front of us. Gigerenzer calls this the “fear of dread risk”: the apprehension about losing a lot of lives within a short time.
Every day, we learn how many people died of the coronavirus around the world. But many of those people would have died in the normal course of events, from a variety of reasons such as heart-attacks or flu. So, the issue is not so much how many people died of Covid-19, but how many more?
In focusing on identified lives, we ignore the loss of “statistical” lives. It is likely that the total impact of that loss will be greater than any loss of lives due to Covid-19. But those deaths will register less on our collective psyche since they will be diffused, scattered all over the world and will not be reported on in the same manner.
Like it or not, there is a trade-off here: how many lives will be taken by Covid-19 (identified lives) and how many lives will be lost due to our attempts to prevent loss of lives from Covid-19 (statistical lives).
In fact, at the time of writing, hospitals in Washington State, which has been hard hit by the virus, are engaged in a bleak triaging of which patients should receive treatment and which should not, since providing everyone with adequate treatment is no longer an option.
A recently released influential paper by Neil Ferguson and colleagues at Imperial College, London suggests: “Two fundamental strategies are possible: (a) mitigation, which focuses on slowing but not necessarily stopping epidemic spread and (b) suppression, which aims to reverse epidemic growth, reducing case numbers to low levels and maintaining that situation indefinitely.”
However, in reality these are part of a continuum: to what extent do we force people to self-isolate, curtail economic activity and reduce social contact? According to Ferguson and his colleagues, we will need to do this for 18 months.
But, bear in mind that we are really dealing with probabilities here. A shutdown of 18 months will work better than a shut-down of six months, which is better than four weeks; each imposing a different magnitude of social and economic costs.
Already, we are seeing a spike in unemployment claims and business insolvencies. We know that unemployment results in significantly lower life expectancy. It will also lead to homelessness and increased poverty. Mental health problems, particularly among children, will rise dramatically. All of these will also take a toll on healthcare systems and healthcare workers. The human cost of job losses and bankruptcies will be massive. Much of the pain of this shut-down will be borne by the socio-economically disadvantaged.
Beyond a certain point, it would just not be worth it to keep the economy shut down in order to save more people. Does the Government (or Treasury) have realistic estimates of how much the economy will shrink, how many jobs will be lost, how many businesses will go bankrupt? How large is the relief package required to prevent an economic catastrophe if the lockdown ends after four weeks or if it continues beyond that? Surely, this calculation should play a role and dictate how long a shut-down we can survive.
The real question here is: How large is the reproduction rate; i.e., the rate at which the contagion spreads? Current estimates suggest this rate for coronavirus is more than two; each infected person is affecting more than two others. We need to bring this number down as far as practicable.
It seems strict self-isolation should be able to achieve this goal. At this point, and I may well be proved wrong, Japan seems to be successful in keeping the spread down while allowing people to go about their business.
It is clear a crucial factor is population density. So a lockdown in places like Auckland or Wellington may make sense. It is not clear to me that large parts of the South Island, with low population density, need to be locked down.
For much of the country outside the large metropolitan areas, we should be able to do what we were doing before. Avoid large gatherings and implement self-isolation as needed. Complement this with public service announcements about good hygiene and the need to stay home if someone believes they may be infected in order to bolster the social norm of self-isolation.
Let people decide their risk-tolerances. Offer all those above 60, those with a history of respiratory problems or ones with compromised immunity the opportunity to work from home, should they choose to do so. Support businesses in providing paid sick leave to these workers over and above their usual entitlements.
What we face right now is a social dilemma; those who have been infected need to make sure that they do not spread the infection. But, evidence suggests Kiwis were and are doing a pretty good job with self-isolation. People who are obviously flouting self-isolation rules are being denied patronage at businesses and at times being reported to the police.
My research suggests people can be quite good at solving such collective action problems; that exhortative public messages asking people to choose cooperative actions can succeed. It may need to be backed up with sanctions for hard-core violators.
At the very least, the Government should track the path of the infection and selectively loosen restrictions in different parts of the country as and when appropriate. Ideally, much of the country should be restriction-free before four weeks have passed.
This will allow us to mitigate both the coronavirus catastrophe as well as the catastrophe of another Great Recession.
First appeared in Newsroom, April 8 2020
As the Covid-19 picture emerges, it is vital to continually assess our response. The virus was identified quickly and tests developed. We are acquiring knowledge about it at a great rate. As cases mount across the world, a picture is also emerging of the effect of the virus on populations, which, as an epidemiologist, is my interest.
Unprecedented social controls have been rapidly thrust upon us. The justification initially was not overloading intensive care facilities, but we have now moved beyond that to “flushing out the cases we already have”. The duration of the lockdown is uncertain. It is also unclear how much of a financial hit the country is willing to stomach.
We know this virus is serious, but exactly how serious? How does the case-fatality rate, a measure of the importance of the disease, compare with other similar viruses?
As a rough guide, the US Centers for Disease Control and Prevention uses rates of between 0.1 to 2.0 per cent to determine how to respond to a new threat. This is clearly an important statistic to attend to, but it is easy to get this wrong – very wrong.
The calculation is skewed, initially, because sicker patients are tested first, making the infection appear more serious. Also, in determining fatalities, uncertainty arises in patients who are otherwise sick with a limited life expectancy, who then test positive and subsequently die. Should they be labelled as Covid-19 deaths?
Remember swine flu in 2009? Initial estimates of case-fatality rates were about ten times higher than those calculated once the dust had settled. It turned out that swine flu, that year’s killer virus, was no more harmful than seasonal flu.
So let’s look at a couple of examples where more comprehensive testing has been completed. The Diamond Princess ship is one of the few examples of a closed population who were all tested for the disease. Seven deaths occurred in 700 test-positive patients, giving us a case-fatality rate of 1 per cent.
Remember, this was an elderly population. Calculations show that, if these rates were translated to a Western country’s overall age structure, the statistic would be 0.125 per cent (interval of plausible values: 0.025 per cent to 0.625 per cent), higher than normal flu (~0.1 per cent), but not by much.
The figures of up to 900 deaths a day in Italy are alarming, and so is the nation’s crude case-fatality rate of 9 per cent. However, a recent analysis of the deaths in Italy shows that only a small fraction were entirely due to Covid-19, occurring in people with no co-morbidities (3 out of 355; 0.8 per cent). Many deaths were hastily labelled as Covid-19 related when they were not.
As the average age of those dying is 80, that is not surprising. This kind of seasonal epidemic of deaths has occurred frequently in elderly populations living in this region for some years.
Another question to ask here is whether Covid-19 represents an added burden on top of usual seasonal viruses. After all, admissions to hospital, intensive care, and deaths occur at a background rate.
Time-series plots of overall deaths in European countries show surprisingly low rates for this time of year, even in heavily affected countries, such as Germany, Spain, France and Italy, even in the over-65 age group. Italy has the most dramatic increase, but no higher than occurred during the same season two years ago.
Is a “lockdown” and closing the borders even effective? Unfortunately, meta-analysis of social distancing measures for avoiding viral chest infections found that such an intervention was not strongly supported, since little evaluation of these policies had been done. Of all the preventive measures that were examined, improving hand hygiene had the best supporting evidence. It remains to be seen whether lockdown will result in “flattening the curve”, but we don’t have strong evidence in favour.
Despite my scepticism, Covid-19 does pose a real risk to our health. Sensible measures include better hand hygiene, ensuring good cough etiquette, and restricting large gatherings. Limiting exposure for the elderly, and people with chronic conditions, makes sense.
It is important that the public health response matches the threat posed to our health. It is important we keep abreast of developments, such as tests of immunity, so that we can return to normality quickly.
We don’t want to squash a flea with a sledgehammer and bring the house down. I believe that other countries, such as Sweden, are steering a more sensible course through this turbulent time.
Simon is a senior lecturer and epidemiologist at the University of Auckland.
Grant Schofield, Professor of Public Health at Auckland University says we need to exit lockdown.
Yesterday morning my teenage boys Sam and Jackson were out riding their bikes. The police pulled them over to question them about what they were doing and where they were going. They explained they were cycling for exercise and staying local. That seemed OK, but they then were told that they were sweating and sweating was dangerous, because it could transmit the virus, so they should avoid that. Wrong of course, but wow, unprecedented police powers that are beyond what New Zealanders have ever seen outside of wartime.
All in the name of eradicating Covid-19. Unite against Covid-19!
So can we achieve this?
The simple answer is no. We could with better tools. But now no.
Director-General of Health, Dr Ashley Bloomfield, recently said there is no plan B. The plan is the plan. In fact, there is strong social pressure to say nothing negative about the war effort. Negative is usually defined as anything off script, no matter how scientific. Look at my colleague Dr Simon Thornley in the last few days questioning the data being used to make our big decisions.
Back to eradication.
To eradicate this virus first, we need to know who has it, with certainty. At the most basic level that would mean that we can know if our elimination has worked. It also allows us to quarantine those who do have it, including all the asymptomatic, so they can’t unknowingly infect others. We would also be able to send those infected and now immune back out into the world.
To know these numbers we need a near-perfect test. One which correctly identifies all those who are infected, or not infected. Any false negatives, those who in reality are sick, but are tested and released as fine, would be particularly problematic. You’d also want to test on a scale with large numbers randomly across the population. That’s the only way you can confidently rule out the existence of the virus.
How does our testing go under this scientific scrutiny?
The best available test is Real Time PCR. A sequence of biochemistry allows for the detection of virus RNA. If you have these you almost certainly have Covid-19. The problem is that a negative test doesn’t mean you don’t have it. In fact, there are limited data on the accuracy (or sensitivity) of PCR for this virus. In China, a small number of patients with clinically compatible illness were tested using PCR and it correctly identified as many as 72 percent and as few as 32 percent and was highly variable in repeat tests. For similar viral testing sensitivity runs at 50-70 percent correct positives.
What is most important is that this means between 30-50 percent of those tested are released back into the community when they are in reality infected.
This is made worse because mostly we just test those with obvious symptoms. It means we won’t catch any of those without symptoms – those we most need to catch. It’s likely we have large numbers of asymptomatic people already in the community unintentionally infecting many others. Data from Iceland show that this might be as high as 50 percent of cases.
Second, we haven’t and don’t have the capacity to do the accurate level of massive population testing we need to. Simple as that.
Third, even if the above were both 100 percent, we cannot tell if you have already been infected and recovered. We need antibody testing to become available for this to be known. This hopefully comes to NZ soon. Eventually it will and we will really know the true numbers of infections. This means we can calculate the all-important “case fatality rate” which is the key number to decode how to react to a pandemic. We really must know how lethal this virus is, and for who, compared to something we already know like the seasonal flu.
To be clear, we don’t know this number with any certainty, and the modelling used to predict deaths, and therefore government responses, depends on this as yet uncertain number. The WHO’s original estimate was 3.4 percent, with the latest estimates looking closer to 0.3 percent and has usually come down further with more accurate measurement in other pandemics. The figures are still very uncertain. Seasonal flu has a case fatality rate of 0.1 percent.
I got most interested in this three weeks ago when I became sick with a sore throat, swollen glands, which eventually changed to a dry cough, difficulty breathing especially at night time, and then a lung infection. Repeated calls to the Healthline and my doctor resulted in vague advice not to worry and “drink more fluids”. Everyone in my house ended up with symptoms, all less severe than me. This really piqued my interest in how we were missing the boat. I had travelled on aircraft and mixed with people from overseas (at Ironman NZ in Taupo). Yet, I was outside of scope for being tested.
Did I, and my family, have Covid-19? I don’t know, and that’s the point.
We were originally on a plan to “flatten the curve”. This means reduce the speed of infection, also called mitigation. This seems prudent given we know we have a potentially lethal virus circulating in our community, with no easy way to accurately detect it. As well, there are probably large numbers of asymptomatic people spreading. Mitigation aims to lessen the potential high demands on the health system so we can give those who need it the best quality of care.
To me, it seems most likely that we cannot contain this because we can’t measure it.
Yet, somewhere in the last week the strategy changed to an eradication policy. Even if full eradication isn’t the goal, if it’s just “seriously flattening the curve” that requires much wider, more accurate surveillance and then quarantine than we have.
Our current strategy has so many questions, but very few answers.
What’s the exit strategy for this eradication policy? When do we go back to work, how do we decide with reliable data, and what then? What do we do if we get more infections again? Do we go back to lockdown? What if we are not successful?
Do we just “try harder” and lock down more? When do we decide to give up and try something else? How much harm is done to health from economic collapse and poverty will we get? How compliant will New Zealanders be in the longer-term? Even a small amount of civil disobedience is essentially unenforceable?
In the end, the goal in public health is to get the best possible outcomes, for the least possible harm, with the tools and resources we have available now. So as more and more data emerge, and we see where we are at we must be willing and able to change our mind, and move in ways that maximise the best health outcomes and the least harms.
Given we currently have no way of identifying accurately enough who has this virus, especially asymptomatic positives, then mitigation is the most logical pathway, especially given the unknown and potentially large harms of extended lockdown. Let’s explore our Plan B. Now is good.