HEALTH & WELFARE

AVOIDING THE

The Japanese government has urged
the public to avoid theThree Cs. A key finding of thegovernment’s retrospective tracing
approach is that these threeconditions facilitate transmissionof the virus.

COMPARISON OF CONTACT TRACING IN JAPANAND IN OTHER COUNTRIESTHREE CS:A KEY TO PREVENTINGTHE SPREAD OF COVID -19

JAPANJapan has been preventing an explosive outbreak of COVID-19 by focusing on avoiding the so-called“Three Cs” (closed spaces, crowded places, and close-contact settings), key findings of its unique approach oftracking back infection routes, while seeking to revive the economy without locking down.
As the long fight against COVID-19 continues,
Prime Minister SUGA Yoshihide, in his first policy
speech, stated that the Japanese government would
do everything it could to continue preventing an
explosive outbreak and thoroughly protect thelives and health of the public. He also spoke aboutadvancing the recovery of the economy through theresumption of socioeconomic activities.
Since the early stages of the COVID-19 pandemic
in 2020, the Japanese government has taken a socalled “cluster-based approach,” which has focused on
finding the source of infection clusters (outbreaks) inorder to prevent large-scale spread. That approach
was adopted because the public health authority

Wearing masks and washing hands, which
are effective means of preventing the spreadof COVID-19, have been customary inJapan since before the pandemic.

Retrospective tracing

discovered early on that much of the transmissionof the virus that causes COVID-19 is propagated by
an exceedingly small proportion of people carrying
it. By tracking past activities of multiple patients soas to identify the common sources of infections, andexhaustively surveying and monitoring close contacts
associated with those sources, further spread ofinfections can be minimized and delayed.
At the end of February, the Ministry of Health,Labour and Welfare established the Cluster-Response
Task Force comprising of experts on infectious
diseases in Japan to develop and implement thecluster-based approach. Working with local
governments where clusters had arisen, the task

Common sourceof infection

Retrospective tracing
In addition to prospective tracing based on the“Characteristics of COVID-19 transmission,” past
activities of multiple infected people are investigated inorder to identify common sources of infection.
Close contacts associated with those sources are thenmonitored closely to prevent the spread of infection.

Prospective tracing
MOST OTHER COUNTRIESProspective tracing
When a case is newly confirmed, close contacts areidentified and monitored for symptoms.

force gathered and analyzed data for use in planninghow to combat the pandemic. At the frontline,
municipal health centers carried out not only
“prospective tracing,” which aims to identify close
contacts of patients to prevent further spread, butalso “retrospective tracing,” which surveys patients’behavioral histories by conducting thoroughinterviews.
“One of our focuses has been retrospective contact
tracing, which tracks past activities of infected people
to discover possible sources of infection and thereby
identify clusters,” SAITO Tomoya, director of theDepartment of Health Crisis Management at theNational Institute of Public Health, recalls. “Thisinvestigation revealed that the ‘Three Cs’ (closedspaces, crowded places, and close-contact settings)
are the major risk factors that could lead to theoccurrence of clusters.”
Since this finding, the Japanese public has been
repeatedly reminded to avoid places and situations
where these three conditions overlap. By declaring
a state of emergency in April and May and callingon the public to voluntarily refrain from leaving thehome unnecessarily, the government successfully
encouraged the wider public to avoid the Three Cs.
Later on, the World Health Organization (WHO)began circulating a global message through social
media encouraging people to avoid the same ThreeCs.
Another notable tool for stopping the spread of
COVID-19 is the wearing of masks. Fugaku, theJapanese supercomputer that has taken the top spotin two consecutive global performance rankings, has
run simulations of the effectiveness of face masks andof how airborne droplets spread in high-risk places
and situations such as restaurants and elsewhere.
Publicly released findings of the research show thatwearing a mask can significantly mitigate the danger
posed by these high-risk settings. In Japan, hygienic
practices such as wearing masks and washing hands,
which are effective means of preventing infections
from spreading, were customary prior to thepandemic, allowing Japanese society to smoothly
adjust to life under the “new normal.”
The fight against COVID-19
is not yet over. In the meantime,
Japan will continue to take thenecessary steps to combat thepandemic, striking a balance
between preventing the spread of
the infection on the one hand andkeeping the economy going on theother.
The simulation using supercomputer Fugaku shows that not wearing a mask (left) fails to suppress theextent to which airborne droplets are spread during actions such as coughing compared to when
wearing one (right).

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