Translation of pp. 35-38 of “Analysis of
the Response to COVID-19 and Recommendation” (May 29, 2020)
<Supplement>
Regarding Japan’s Cluster Response
o
As stated in the main document, “Cluster
Response” refers to conducting a proactive epidemiological survey so that we
can capture the beginning of a cluster (such as the source) and take measures
early to slow or minimize the transmission. In our country, by implementing an
“effective cluster response”, the following impact was achieved:
1. We were
able to prevent a massive outbreak that could have resulted from a chain of
clusters
2.
Early on, we were able to identify the “place”
of “3Cs (Crowded place, Confined space, and Close conversation)” as the
common source of transmission as a result of the proactive epidemiological
survey conducted. Because we worked to inform the public to avoid the “3Cs”
with reference to relevant factors such as speaking loudly and singing, we were
able to effectively appeal to the public to avoid environments that would have
put them at a higher risk for forming clusters.
3. By
following links of cases based on clusters, we were able to estimate the status
of transmission in various regions more accurately. This meant that we were
able to determine the increase of “isolated cases” as increase in transmission
in that region, which allowed us to respond quickly in those regions.
o
There were 2 unique characteristics.
(1) We were
able to detect the transmissions originating in China (first wave) and
transmissions originating in Europe (second wave) early
o
In the first wave that occurred between
January ~ February originating in China, 149 cases were reported by February
25, including clusters, as a result of implementation of cluster response, etc.
by hokenjo or health centers of local administrations. (5)
|
Cumulative
cases |
Japan |
Germany |
France |
UK |
US |
Italy |
South
Korea |
Taiwan |
|
Through
2/18 |
60 |
15 |
12 |
9 |
15 |
3 |
31 |
22 |
|
Through
2/25 |
149 |
15 |
12 |
13 |
53 |
229 |
892 |
30 |
o
One of the things that enabled early
reporting is that guidelines for surveillance for detecting an unknown
infectious disease, etc. had been reviewed in preparation for the
Olympics/Paralympics, and we had asked for wide reporting of cases in advance.
o
On the other hand, developed countries
such as European countries other than Italy and the U.S. that were already
seeing serious local transmissions had not detected many local transmission
cases by this time, as shown on [Chart 1. Trend of new cases in other countries
(by date of reporting)].
o
In reality, it is likely that there had
been transmissions occurring under the radar in these countries, but it was not
yet visible. By the time it had become visible, which was after mid-March,
rapid increase in transmissions in both Europe and in the United States were
occurring.
o
Japan was able to detect transmissions
early. Another reason why this was made possible was that Japanese citizens have
good access to healthcare even in rural parts of the country. Physicians were
able to order chest X-rays, CT scans, and PCR tests when they suspected
COVID-19 from symptoms presented, such as fever and respiratory symptoms. This
allowed early detection of transmission.
In fact, the first local transmission case reported on January 16th
was a case in which the physician suspected COVID-19 and ordered a PCR test.
(2) Effective
cluster response was implemented
o
As noted in (1), Japan was able to detect
new cases and clusters
earlier than other countries. Through accumulation of
these cases, the Expert Meeting already knew, as published on our view on March
2nd6, that regardless of the
severity of the symptoms of patients, about 80% of cases were not infecting
other people. Early on, we knew that COVID-19 had clearly different
characteristics than the influenza virus (one patient likely to infect others).
o
What this means is that COVID-19 was
spreading largely via creation of clusters. We had supposed that if we can
suppress clusters (within the area where cluster response can be implemented),
we can suppress the increase in transmissions overall.
o
In addition, from early proactive
epidemiological survey, we had been able to analyze the places where clusters occurring.
This enabled us to implement an effective response measure, “Avoid 3Cs”, which
was not implemented in other countries.
o
Contact tracing deployed in other
countries takes new cases as a starting point. Then you figure out every person
who have had close contact with that case and find future cases. This is a
“prospective” investigation.
o
“Prospective” investigation was conducted
in Japan too; however, based on the known characteristics of this virus, when
we found multiple cases, we looked carefully to see if they had common sources.
In other words, when we found a case, we went back in time and identified the
“place” that was the common source of transmission. This is a “retrospective”
investigation. This also enabled us to find the concept of “3Cs” early on.
Also, for those who were present at the same place (common source), we put
effort into conducting proactive epidemiological survey. Such “retrospective”
contact tracing was based on methods that had been done for tuberculosis
patients through health centers of local administrations.
o
What was unique about Japan’s response was
that based on “retrospective” contact tracing, we went back to the source of
the infection and made sure that we did not miss the chains of transmissions
that followed. Focus was on ➀
identifying the source early on, ➁
identifying those who are related to the source early on, and as a result, ➂ early
treatment of patients, and ④ early
implementation of response measures to suppress increase in transmissions.
o
As we have described, Japan was able to
estimate the transmission status in each region by mainly following the links
of cases in clusters. This enabled us to determine that the increase in
isolated cases without known links would suggest an increase in transmission in
that particular area. This enabled us to strengthen response measures early for
each region.
o
We know at this point through genetic
analysis that imported cases have had major impact on spread of local
transmissions as well. What this means is that, as a result of having a larger
number of imported cases as a second wave originating in Europe, etc., isolated
cased in various regions increased. As the number of new cases increased and
number of isolated cases without known links increased, we had no option left
but to declare a state of emergency on April 7th.
6
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