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

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

Contents
1. At least 100,000 people will die if it doesn’t work
2. Rationale for cluster measures
3. The state of success of the cluster measures
4. Detection of clusters and a “one month round trip time difference”
5. Can “invisible clusters” be detected with enhanced inspections?
6. What should we do?
+ Reference material

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

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

If Japan’s population is 100 million or 40% infected, 40 million patients. Of the 40 million people, 20% = 8 million will become seriously ill, and 5% = 2 million will become severely ill(people who will die if they are not managed in the ICU).
The number of hospital beds in Japan is about 1.6 million, which is usually 80% to 90% full, so it will never be possible to meet this much demand.
The mortality rate of infected people is estimated to be 0.6–0.3%, so a minimum of 120,000 deaths. In Wuhan, the mortality rate is 3.8 percent, which means that the mortality rate jumps tenfold when the capacity of medical institutions is exceeded. If that were to happen, assuming 3%, there would be 1.2 million deaths.
Left: # of new positive cases by age. Right: # of severely ill cases
[The following is Yoshimine(the author of the original article)’s interpretation] About 220 elderly people and 50 young people will be severely ill per 100,000 people. That’s 270/100,000 people, so 100 million would be 270,000 people. This is the number of severely ill people (people who will die if they are not managed in the ICU), not the seriously ill. So, there are only 10 ventilators/100,000, or about 10,000. Moreover, this graph shows the number of newly infected people (3,500,000/100,000, or 3.5 million if you look at 100 million people) and the number of seriously ill people, so 250,000 is not cumulative.
I may be wrong in my understanding, but if we combine my layman’s calculation of 2 million serious cases with the fact that the capacity of ventilators to save lives is only 10,000 people or turnover, we may be looking at 2 million deaths.

(2) Strangely low Japan’s 𝑅₀

Needless to say, that otaku line is a joke. I’ve been exposed to a larger number of people than I expected, so I’m making a tactless comment.

2. Rationale for cluster measures

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

The above is how flu spreads. The below is how SARS-CoV-2 does.

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

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

The one thing that is common to all the places where outbreaks have been confirmed so far is
(1) It was an enclosed space with poor ventilation
(2) There were a lot of people in close proximity
(3) Conversations and vocalizations took place at close range (within reach of each other).
This is where these three conditions overlap at the same time. It is likely that more people would have been infected in these settings.
Hermetically sealed, compact, close.
Enclosed space, congested place, close scene.
(1)Enclosed spaces with poor ventilation, (2)congested areas where many people congregate, and (3)close situations where close conversations occur.
For example, on a crowded train, there are two ways of doing (1) and (2), but (3) is not often done. However, in some cases, (3) may overlap. (March 9 expert meeting opinion)

3. The state of success of the cluster measures

The official view is that the three pillars are as follows
(1) Early detection and early response of clusters (patient populations)
(2) Enhancement of early diagnosis of patients and intensive treatment of critically ill patients and securing of medical care delivery system
(3) Transformation of citizens’ behavior
However, the second half of (2) is somewhat heterogeneous, so it’s better to consider it in a separate frame. The first half of (2), “early diagnosis,” should also be viewed from the public health perspective of detecting clusters early, rather than from the medical perspective of providing the best possible treatment. Even if a corona infection is diagnosed, only symptomatic treatment is available.If quasi-suppression by cluster measures is not successful and leads to an explosive spread of infection, the health care delivery system will physically collapse, which is inevitable.

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

(1) The role of PCR testing

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

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

Half of the 100 million people, 50 million, are eligible young people. Right now there are thousands of infected people in Japan (the official reported number of cases is 892); assuming there are 10,000 people, that’s 0.01%.
Out of 50 million young people, there are 5,000 infected, so if we test 1 million people, there are 100 infected and 999,900 uninfected. Let’s make it a million non-infected people because it’s troublesome.
The PCR test is said to have a sensitivity of 80% and a specificity of 99%, but let’s make both 99% in the service.
Out of 100 infected people, 99 will test positive and one will be negative (false negative).
Of the 1 million uninfected people, 990,000 will be negative and 10,000 will be positive (false positives).
If you do that, there are 100,099 positives, so we don’t know who those 99 infected people are after all (the positive rate is 1%).
@BikkuriSeitai “ Would a drive-through test with a CT-equipped vehicle be effective as a supplementary measure?” @georgebest1969 “It is invalid for now. This is because the clusters in Japan are limited in some spots and not as regional as the Korean ones. Hokkaido cases are a bit regional, but even there the number of infected people is so low that cost-effectiveness (of the testing) is not balanced.”

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

6. what should we do?

(1) Worrying situation (as of March 21)

(2) Two-way risk communication

It’s a dire situation that makes you want to cover your eyes if you fail. There is a glimmer of hope in sight. The “Japanese model” seeks to find long term sustainable options while maintaining minimum socio-economic functions, eliminating waste, and saving the socially vulnerable from being crippled. I believe there is an optimal solution there, but it may not be an easy concession for the public. There needs to be a process for everyone to agree. (It’s a kind of mean translation, not a verbatim transcription.)

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

Hermetically sealed, compact, close
Enclosed space, congested place, close scene
Enclosed spaces with poor ventilation, congested areas where many people congregate, and close situations where close conversations occur.

Reference material

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Shota Mizukami

Shota Mizukami

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