The Japan model

So what is the Japan model? First, it is a cluster-based approach, derived from a hypothesis obtained from an epidemiological study based on Chinese data and conducted on the Diamond Princess cruise ship that entered the port of Yokohama on February 3, 2020. This hypothesis accounts for the many passengers who were not infected with the coronavirus despite having had close contact with infected persons. It posits that the explosive increase in infected persons is a result of the high transmissibility of certain infected individuals, which forms a cluster. Infected individuals with even higher transmissibility appear from these clusters to form more clusters and infect many others. Based on this hypothesis, under the cluster-based approach, each cluster is tracked to the original infection source and persons with high transmissibility are isolated to prevent the spread of infection. For this reason, pinpoint testing is carried out and broad testing of the population is not required, in contrast to the approaches taken in other counties.

This cluster-based approach is conditioned on an environment in which there are only a few infected persons and clusters are detectable at an early stage. In February 2020, when the spread of infection was observed in Hokkaido, a cluster-based approach was adopted. As a result, Hokkaido was successfully able to contain its outbreak.

For the cluster-based approach to be effective, protective measures at airports and ports are important. Hokkaido has the advantage of being an island, making it comparatively easy to control the inflow of infected people. Behavioral changes are also required. On February 28, 2020, acting without legal basis, Hokkaido Governor Naomichi Suzuki declared a state of emergency and called on residents to refrain from going outside. Residents took the call seriously, and are responsible for the success of the cluster-based approach. Following its success in Hokkaido, the cluster-based approach was adopted nationally. On February 25, 2020, a Cluster Response Team was established in the Ministry of Health, Labour and Welfare.

Here is more from Kazuto Suzuki, with other points of note.