How Japan is combating SARS-CoV-2/Covid-19

Disclaimer: The following is a translation of this article issued on March 20th. The original article was written by a lay lawyer, not a medical expert. It, however, seems so far the most comprehensive article describing SARS-CoV-2/Covid-19 situations in Japan and answering common questions, based on arguments made by medical experts. The translation was first made by a machine-learning and I tweaked the output a bit to communicate better. I didn’t bother to correct English and scrutinize minor errors.

Explanation of the “cluster countermeasures” of the expert meeting — The last hope to deal with the new coronavirus

The explosive spread of COVID19 in Wuhan has led to an explosion of infection in Europe and the United States, with no end in sight. Although Japan has not yet seen the explosive spread of the disease as in Wuhan, Europe and the United States, it is still walking a tightrope.

At present, the Ministry of Health, Labor and Welfare’s Council of Experts and the Cluster Response Team are playing a central role in combating coronaviruses in Japan. Both of these organizations, with top-notch scientists, seem to have designed and implemented a workable strategy — “counter-cluster”. The cluster measure is Japan’s last hope for surviving this disaster while avoiding a catastrophe, but the full picture is not clear because it seems to have failed to get enough publicity.

This article explains the facts and rationale of the cluster measures based on my understanding as a lay lawyer, relying on published materials (especially materials from expert meetings, press conferences, and notes by Professor Minato Nakazawa). The target audience was supposed to have a fair amount of prior knowledge, but it might be a good read for many. However, try searching elsewhere for what 𝑅₀ (Basic Reproduction Number) is, or for the pathology of COVID-19.

1. At least 100,000 people will die if it doesn’t work

(1) What happens when there is an infection explosion?

Infectious disease control strategies can be broadly divided into containment (Suppression) and mitigation (Mitigation).

If containment fails, the infection spreads exponentially and is eventually terminated by the acquisition of population immunity or herd immunity. The population immunity is when a certain percentage of a population becomes infected and acquires immunity so that no further infections can be spread within that population. The percentage of individual immunity required for the immunity is determined by 𝑅₀, and is estimated to be 40–70% for COVID19.

We have already failed to contain it.
The theory is that the spread of the new corona infection is inevitable and that eventually, we will have to settle for the acquisition of population immunity (or at least mitigate the damage). That said, despite the failure of containment, there are those who make the bizarre claim that there is a way to avoid the spread of infection. That is the Council of Experts/Cluster Measures Group, whose claim is “containment through cluster measures”. This is a bizarre strategy made up of the strange nature of the new Coronavirus, a strategy that could be called “quasi-containment”.

First, let’s look at how much of a sacrifice it takes to get to population immunity. First, I’ll do my own calculations.

Let’s take a look at some more sane estimates. This is the latest expert meeting material.

Incidentally, Professor Nakazawa said that if the cluster measures failed, “the worst-case scenario of 150,000 people dying would become a reality”. It is said that. This does not take into account the aforementioned 10-fold effect and ventilator limitations.

Postscript: This is a must-read, easy-to-understand explanation of the world’s movements. It’s a mitigation strategy and a suppression strategy. The latter lowers 𝑅₀ to near zero due to urban blockades. Japan’s “quasi-containment” strategy has a goal of 𝑅₀<1.

(2) Strangely low Japan’s 𝑅₀

It is also necessary to press the fact that Japan’s 𝑅₀ was low compared to other countries. This is a very strange thing, but it is probably true. If it had been the same level of 𝑅₀ as in Europe and the United States, there would have been an overshoot (infection explosion) situation in February like in Wuhan and the United States today. Trends in the number of people infected, seriously ill, and killed in Japan have shown a consistently low 𝑅₀ since January.

In contrast, there is some doubt that this is due to Japan’s relative lack of testing, but it would only have the effect of shifting the exponential increase by a few days, which does not explain the consistent loose slope since January.

Why is 𝑅₀ low only in Japan without any specific measures (Singapore and Hong Kong have very strict measures)?. This is a mystery, but there’s no point in prying. Government measures such as anti-cluster measures are not the cause (it must be a factor that has been present since January).
This is probably due to the ingrained personal protection of handwashing and masks, the lack of physical contact habits such as handshakes and hugs, and the fact that many otaku are withdrawn and live in two dimensions.

If 𝑅₀ was originally high (in line with other countries), it was probably not feasible to implement measures to improve 𝑅₀ to <1 in cluster measures.

2. Rationale for cluster measures

In the big picture, Grantz K, Metcalf CJE, Lessler J (15th Feb 2020) Dispersion vs. Control. is the basic framework for the Nishiura H et al. Closed environments facilitate secondary transmission of coronavirus disease 2019 (COVID-19) has laid out specific measures based on it.

(1) Characteristics of COVID19 propagation — large variance of 𝑅₀ (Grantz paper)

The Grantz paper showed from the Wuhan data that coronaviruses have a large variance of 𝑅₀. A lot of infected people don’t generate secondary infections, which would seem to make them less contagious, but they don’t. The reason why it is so contagious is that a very small percentage of infected people create large secondary infections (source of the quote below).

Influenza causes a near-average number of secondary infections, which are spread gradually and continuously. Most people who are infected with COVID19 do not generate secondarily infections, but a small number of people with the virus cause large secondary infections that can be spread “all over the place”. A large secondary infection, caused by a small number of infected individuals, is a cluster infection.

The spread of Covid-19 is a discrete/non-linear process, while influenza is (similar to) a linear process. It has its own tricky and unpredictable aspects, but there is room to intervene successfully.
In theory, if cluster infections are somehow deterred and suppressed, then 𝑅₀<1 can be achieved because there are relatively few other infections.

(2) Elucidation of the causes of cluster countermeasures (Nishiura paper)

The Grantz paper showed that a state of 𝑅₀<1 can be achieved by controlling cluster infections, i.e., bringing the epidemic into containment.
However, without concrete measures to control cluster infections, it’s a picture-perfect mess.
The Nishiura paper shows the means to do so. Professor Nakazawa described him as a “genius”.
The paper analyzes 110 cases of infection (belonging to 11 clusters) that occurred in the country up to 2/26. The chart below shows the distribution of 27 cases of secondary infection (this chart itself was reprinted on the website of the Ministry of Health, Labour and Welfare with a commentary).

These clusters are due to close contact in indoor environments, such as fitness gyms, riverside restaurants, hospitals, and snow festival tents.
And, as shown in the diagram, the source of infection causes far more secondary infections when it is in a closed environment than when it is not. Unless you are in a closed environment (the white bar), very few secondary infections occur, and only one or two at most. Being in a confined environment has caused secondary infections on the order of 10 people (the gray bar). That is, one of the prominent causes of clusters is a closed environment. The closed environment has an 18.7-fold (95% CI: 6.0, 57.9) risk.
However, what is shown in this (unrefereed) paper is just a closed environment. If cluster infections occur in a closed environment, then a packed train in a large city like Tokyo is a great incubator for cluster infections. There should have been an explosive infection long ago. The trend is that cluster infections do not occur on packed trains.

(3) The three conditions of cluster infection: closed, dense, and close.

Based on various data (you will have seen the data after 2/26 in the above paper) and based on our experience, the three conditions were derived by the cluster countermeasures team: closed, dense, and close. I assume that the analysis of a refined mathematical model is not yet complete.

This was made clear in the expert conference opinion on 3/9.

These three conditions account for the fact that cluster infections have not occurred on packed trains (they would have). Packed trains meet enclosed and dense conditions, but people don’t talk face-to-face. They do not meet the conditions of closeness. It’s an extremely counter-intuitive and strange quality, but it’s a fact.

Postscript: There was an introduction of micro droplet infection on NHK special. According to this, micro-splash is likely to drift in even on a crowded train.

If all citizens can comply with avoiding the three conditions (which is extremely easy compared to the lockdown/urban closure implemented in Wuhan, Europe and the United States), you can expect to be able to cut secondary infections in closed environmental cases in the gray bar of the figure in the Nishiura paper.
In other words, relatively easy behavioral change can prevent cluster infections (but not prevent infection. This difference is the essence), and it can contain the majority of coronal infections.

3. The state of success of the cluster measures

Counter-cluster measures are two-pronged.
(1) Early detection and early suppression of already occurring clusters
(2) Prevention and suppression of cluster outbreaks through behavioral change

What does it mean to be in a state where the cluster measures have been successful?

Because citizens avoid the three conditions, cluster infections rarely occur. Other infections other than cluster infections (e.g., workplace, packed trains, etc.) do occur, but they are formidable. This is because simple infections alone, excluding cluster infections, would taper off, with 𝑅₀ far below 1. Clustering measures are not about containment of infection. It is the containment of cluster infections.
That said, since there are people newly infected with the virus without isolation in the city (there are apparently thousands of them in Japan right now), infections do occur, and cluster infections may occur by some mistake.
Cluster infections that have occurred need to be detected early and controlled at an early stage. That’s because cluster infections can lead to an explosive spread of infection if cluster infections.

4. Detection of clusters and a “one month round trip time difference

(1) The role of PCR testing

The primary means of detecting clusters is PCR testing in critically ill people (mainly the elderly).
Coronavirus is characterized by the fact that younger people are less severely ill and often end up with mild or asymptomatic illnesses (the opposite in older people). In other words, clusters made up of young people are “invisible”. Although juvenile clusters pose little health risk to the individual, they can cause a chain of cluster infections without being noticed, and if noticed, it may be too late. This is the scariest thing.
If an elderly person is included in the cluster infection, he or she will become seriously ill and have to undergo a PCR test (such cases are relatively common), and will eventually be caught in the detection network of the cluster task force, although there is a time lag.
In addition, the detected cluster data can be analyzed to further refine and ensure the identification of the conditions under which clusters occur. Detection and suppression and behavioral transformation need to be implemented as such a cycle.

(2) Time difference of one month between the two countries

What you need to be aware of is the time lag in detection (cited in the figure).

This figure is for Wuhan, but the yellow bars on the right show the number of cases of infection reported, and the gray bars on the left show a record of the date the case developed. The gray is what is actually happening and the yellow is what the authorities know. It takes approximately two weeks to get from infection, onset, to severity, testing, and reporting. The case count data that we see every day is the reality of two weeks ago.
In Wuhan, a lockdown (urban blockade) was put in place as the number of cases began to increase exponentially, but at that point the exponential increase had lasted two weeks. With the lockdown, the increase will start to decline, but we won’t know the effect until two weeks later, and two weeks can only be spent watching the exponential increases already occurring continue to be reported.
It’s the same situation in the West today. When we saw that the explosive spread of infection had begun, we went to intense measures such as lockdowns, but we had to accept the exponential increase that had already been going on for a while. This is a definite future.

It is very difficult and frightening to deal with an object that exhibits exponential behavior when it can only be observed in the past two weeks ago. Also, if you look at the reality of two weeks ago, and you implement some measures, the effect can be observed again two weeks later.
The cluster measures were implemented at the end of February and the three conditions were made known at the beginning of March, but the data that we are looking at at this time, the data for the second half of February, is only a reflection of the reality of the first half of February. And we’ll have to wait until around March 10 to see the effects of this timing measure. There is a “one month time difference”.

That’s why the cluster task force is so impatient. If you make a mistake, you won’t know it until two weeks later, and the effects of the measures will be seen in another two weeks. In the meantime, the exponential explosive spread of infection may get out of control.
That’s why we need to speed up the distribution of information. Testing capacity needs to be expanded to allow PCR testing to be performed earlier (preferably in patients with minor illnesses), and the reporting process needs to be streamlined to reduce time lost and to track contact persons more quickly. We’re going to need people to do that!

5. Can “invisible clusters” be detected with enhanced inspections?

There is an argument to be made for stronger inspections, following the success of Korea.
There is a need to strengthen inspections, and the government and expert meetings have made that clear, but the question is what to use the inspections for (the purpose of the inspections) and the inspection strategy.

There’s a lot of discussion about whether to increase or curb testing, but it’s confusing. It does not make much sense to argue in the framework of increasing/curbing inspections without a clear inspection strategy. The left/right ideological divide and anti-Koran sentiment are also noise. The inspection strategy should be the first priority.

(1) Options for inspection strategies.

There are three possible inspection strategies:

(a) Examination of the patient
Examination of a pseudo-case patient with pneumonia, etc. and suspected coronal infection

(b) Inspection of the contact person
Active epidemiological surveillance of confirmed infected individuals and those with a history of contact

(c ) Strategy for mass inspection of young people
Testing a large number of mildly ill and asymptomatic patients (i.e., all those who want to), mainly young people

(a) and (b) are the inspection strategies taken by the current Japanese government. (a) isolate corona-infected patients from mainly critically ill patients, and (b) detect and control the cluster by following the contact link and conducting tests.
In contrast, the strategy of mass testing of young people in (c ) is that cluster detection via the occurrence of serious illnesses is circumventive and that the mildly ill or asymptomatic individuals who constitute the “invisible cluster” should be tested directly. The argument that we should emulate Korea seems to be vaguely assumed.

(2) The strategy of mass testing of young people does not work

However, (c ) the young person mass inspection strategy does not work. It will go bust. The reasons for this are the following three points, but essentially the prior probability is low.

(A) A large number of false positives, increased noise, and cluster detection does not work.
(B) The occurrence of false-positive results in a significant medical or isolation facility load.
(C ) You don’t have the resources to implement the strategy. Or even if it is, it’s too much of a burden.

If you do the math specifically, it’s easy to see that it won’t work.

What’s more, there is a problem with the treatment of about 10,000 positive people. Hospitalization is out of the question, and the burden of a dedicated isolation facility would be enormous. 99% of what we call home isolation is useless isolation. If anxious positive people rush to the hospital, the scene will die.
Even if we assume a super test with a sensitivity and specificity of 99%, (A) it cannot be used for cluster detection, and (B) it places an unnecessary burden on medical institutions and isolation facilities.
Moreover, the resources (especially laboratory technicians) to perform (C )1 million inspections are unavailable. Even if it could be found, it would be useless. There are other things that need to be done.
In short, tests with low prior probability should not be done.

Note: Please see also the comments of Professor Nakazawa on the examination. The concept of sensitivity and specificity seems to be quite difficult. Also, there are scattered claims that the specificity is 100% in principle of PCR testing, but it is beyond my ability to follow the academic debate on the estimation of specificity.

(3) Why did Korea do so well?

However, South Korea has successfully contained the epidemic by conducting a large number of inspections, including drive-through inspections. Why is it working so well? (Note: The graph is from the Korea CDC. Why do people distrust Korea just because they write that it is doing well…….. Of course, I’m not sure what will happen next).

First of all, there is a premise related to (C ) that Korea, which had experienced MARS, had strengthened its inspection capabilities in advance. It is probably not possible for Japan to immediately increase its inspection capacity to Korea’s level, and even if it were possible, it would be quite impossible.
Next, regarding both (A) and (B), there is a special situation in Korea where the prior probability was very high among young people in a particular region.
In Korea, mega-clusters have been formed among religious groups, mostly young people. Young people in the Daegu area had an unusually high density of infected people.
In the South Korean case, there were more than 3000 positive young people, but I think less than half of them were infected (even assuming the outrageously large 1% infection rate, that’s about it).

Note: See also Professor Iwata’s tweet about the drive-through inspection in Japan.

(4) Increased inspection capacity and no change in inspection strategy

The current testing strategy of (a) testing the seriously ill and (b) testing the contacts derived from them should not be changed.
Expanding testing capacity and extending the scope of testing for the seriously ill, and ideally to the mildly ill, should be done, as it will speed up the detection of “invisible clusters”.

6. what should we do?

(1) Worrying situation (as of March 21)

As of March 21, the “last hope” for successful quasi-containment with cluster measures is in sight, but concerns leading to an explosive spread of infection cannot be dismissed.
I think there are two major concerns at this point. The question is 1) whether the spread of the infection in Osaka and Hyogo can be controlled, and 2) whether the mood of self-restraint has receded.

In relation to (1), the problem we had a while ago was Hokkaido. I haven’t followed the details, but it seems that the infection has spread and nearly spun out of control in the wake of the Sapporo Snow Festival. Specifically, there was an increase in the number of infected people (unlinked infected people) who didn’t know from whom they were infected (this is a sign of an increasing number of unseen clusters).

However, the governor of Hokkaido decided to declare a state of emergency and, in cooperation with the cluster task force, succeeded in controlling the spread of the infection (detailed explanation is provided in the materials of the expert meeting on March 19). We call this the “Hokkaido Model”.
Currently, Osaka and Hyogo prefectures appear to be in a similar situation. The cluster task force also seems to be discussing countermeasures, but coordination with the governors of Osaka and Hyogo prefectures does not seem to be going well. Even the governor of Omura and the mayor of Kawamura are cooperating with each other, so I hope that they will put aside their peacetime hurdles and cooperate with each other.

Prime Minister Abe’s decision to close schools en masse was made without consulting the Council of Experts/Cluster Task Force. The members of the Council of Experts have criticized it quite harshly, and Professor Nakazawa has assessed it as a “foolish measure”. However, there were no in-depth comments at the press conference of the experts’ meeting or otherwise. We can’t afford to fight with the government.
I was wondering if it made sense to change society’s mindset to say, “This is a big deal”. However, when it was reported that the decision not to extend the school closures was made, it seems that the students’ sense of crisis was relaxed because they felt that “they were safe now”. The weather was good, and the crowds were considerable for three consecutive holidays. It looks like there will be large scale events.
With this relaxation of the self-restraint mood, new clusters may continue to emerge. It seems that the three conditions have become reasonably popular, but we lack experience and data on how strictly they need to be operationalized.

(2) Two-way risk communication

The essence of the strategy of the Council of Experts and the Cluster Task Force was to identify the three conditions of “closed rooms, dense and close together” and to find a solution to change citizens’ behavior by making them aware of the three conditions.
If this anti-cluster theory is correct (and will be further validated by data), Japan’s literal ups and downs depend on whether we, the general public, can abide by the three conditions. Also, from the perspective of the Expert Council/Cluster Task Force, the key to success is risk communication with the public.

However, the risk communication of expert meetings is never enough.
When the announcement was made on Feb. 24 that “the next week or two are on the brink of rapid expansion or convergence,” I was left to wonder how much sense there was in buying time for a week or two, even as I swallowed that it was true if the experts said so.

On February 24, there was a move to set up a cluster task force, which was set up the following day on February 25. The identification of the three conditions is a little after this, using data up to February 26, with information coming out on March 2 and 3. A clear official announcement was made on March 9.
In other words, we set up a cluster countermeasure team, put it into practice, analyzed the data obtained to identify the three conditions, and immediately went on a whirlwind of public relations activities. The speed of the film is nothing short of miraculous. There is no publicly available information, but it is likely that Minister of Health, Labour and Welfare Kato showed leadership and proceeded in a top-down manner.

The first time I came into contact with the information on cluster measures was on March 12 (interview with Dr. Imamura), and on March 13 I watched the video of the interview between Dr. Omi and Dr. Yamanaka (published on March 8), and finally grasped the outline, and on March 16 I went to Dr. Nakazawa’s website and came to the understanding that I am writing in this paper.

Anti-cluster is a bizarre strategy that takes advantage of the strange nature of the virus. It is hard to understand, contrary to conventional theory and common sense. We have been sending out information at a frightening speed, with the hastily prepared cluster task force taking control of the clusters in the field, but even so, we have not been able to develop and implement the public relations strategy necessary to inform the general public. A public relations system will be put in place, but speed is life in the fight against this virus.

The Council of Experts/Cluster Task Force is under tremendous pressure, with limited resources, to fight the virus. It’s a shameful term to use, but intellectuals in the field should support the fight against the virus by actively digesting information and promoting risk communication. You can’t just sit around waiting for information.

At the press conference on March 19, Professor Nishiura’s expression was painful.

In time (or is it now?) The public could be forced to make a serious commitment. The three consecutive holidays were well attended and some high-risk activities were seen. If the current situation in Osaka and Hyogo prefectures does not improve, even a total lockdown of the wider Kansai region will be necessary.
With the explosive spread of infection in Europe and the United States, it appears that this battle is set to be a long one. Without public understanding, you can’t win a cluster infection. What and how do we limit what we do and what are the prospects after we put up with it? What awaits us if we don’t put up with it. Simply concluding that people should wash their hands and avoid the three conditions may not move them.

If you have read all of this lengthy NOTE and can reasonably understand the troublesome story of 𝑅₀ false positives, you definitely understand coronavirus and cluster countermeasures better than the national average. You may be responsible for the cluster infection of knowledge.
You don’t have to be on the same page as me. We need to do what each of us can to raise the level of understanding among the people as a whole. Engineers contribute through open source projects. It can be tough for laypeople with no knowledge of medicine or infectious disease control, but even so, the first step in building social consensus is for the knowledge layer, whether literate or literate, to understand the situation.

I often feel that the coronavirus debate has been influenced a lot by political positions. When Prof. Iwata came on board the Diamond Princess and revealed the truth, there were a lot of people who treated him like a hero without knowing much about the situation, and there were also a lot of people who assumed he was the intruder who messed up the scene and messed up the risk communication. Depending on where you stand politically, the way you perceive will change.
Avoiding an explosive spread of infection is a common interest, regardless of political stance. In the event of an explosive spread of infection, the entire country would sink together and a huge number of deaths would occur. We need to look at the facts of this matter calmly and without turning it into a political dispute or a discussion about the left/right ideological divide / anti-Korean sentiment.

(3) As an ordinary citizen — Let’s keep the economy running under the three conditions

The fight against the coronavirus is going to take a little longer. I think you can see in the news that the US and Europe are in a lot of trouble. We are in a wartime situation.
There are two things that the public can do. It’s a balance between (1) protecting yourself by washing your hands and gargling, and (2) not taking the risky actions involving the three “close” conditions* to avoid infecting people, but still turning the economy around to that extent.
*1)Enclosed spaces with poor ventilation, 2)congested areas where many people congregate, and 3)close situations where close conversations occur.

While explosive outbreaks of infection have occurred in Europe and the United States, Japan has not become as serious as it seems. Some people say it’s because they haven’t been examined, but if more and more people are in the hospital and they’re dying, it’s not something you can hide. It seems that Japanese people take hand washing and gargling seriously. Let’s continue to wash our hands and gargle more thoroughly as we have in the past.

The other thing is to be prepared to not infect people. This is especially important if you are a young person. There are many young people who have been infected with the coronavirus, but are doing well with no symptoms. In fact, you may be one of them. All of us need to take care not to infect people with the idea that they might get infected.
In China, Europe and the United States, they have implemented very strict measures such as lockdowns, where shops are closed and citizens are banned from going out. In Japan, excellent scholars have analyzed the data and found that the spread of the coronavirus can be prevented by avoiding the three conditions of confinement, density, and closeness.

If all events and drinking events were banned, it would be stuffy and more and more people would have trouble making ends meet, but if there were only three conditions, it wouldn’t be so difficult to keep them and the economy could be revived. If that helps us avoid urban blockades and explosive outbreaks, all the better.

However, the data isn’t perfect, so let’s operate cautiously for a while. Even if it’s sealed and dense, as long as it’s not close (e.g., if it’s masked), it should be okay in theory, but I’m a little concerned. If possible, try to avoid all three by ventilating and reducing the density of people.

Some industries, such as entertainment and drinking establishments, can be burdensome, but with some ingenuity, you may be able to find a way to make a living while avoiding the risk of cluster infection.
I’m sure there are many ways to do it. For example, I’d like to have a drinking party, but I can’t eat and drink while wearing a mask. Why not wear a handkerchief or scarf like a mask, or use a face veil? It’s safer to order one person at a time, not share the food, because there is a contact infection.

Reference material

There are three main points on which I have relied for my understanding of cluster measures
(1) Published materials of the expert meeting
(2) Video of the press conference and interview with Professor Yamanaka
(3) Web site of Professor Minato Nakazawa (Kobe University)

I think the video of the press conference and the interview (2) is a must-see in the current situation where it seems that due to resource constraints, risk communication has not been fully implemented.

Find the other references in the original article.

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