t is safe to say that the measures taken by Japan during the Covid-19 pandemic have so far delivered relative success. At the time of writing, we have seen 903 deaths, which makes the mortality rate 0.72 per 100,000 people. This is one-eightieth that of the UK (60.14) and is lower than any other G7 country. Thanks to the fact that the rate of new patients is also low and steady, Japan lifted its state of emergency on 25 May. There has been a lot of trial and error (take the Diamond Princess cruise ship case, for example, over which Japan was exposed to much criticism). Yet since what we consider to be the first wave was dealt with without any lockdowns or curfews, we are often asked for the secrets of our initial success. Time-consuming public health work The first principle of controlling an emerging disease is to detect the outbreak and respond early. Understanding the transmission dynamics through field investigations is key. Japan is fortunate to have 469 local public health centres with more than 25,000 staff, who have been working hard to conduct contact tracing even before the virus became prevalent in the country. With no tracing apps (given patients’ reluctance to disclose full information), contact tracing has been somewhat analogue and time-consuming, involving calling patients and politely asking them to name the people they have met with in the last fortnight. But the system has worked well, and has resulted in an effective “cluster-focused” approach. Pinpointing “clusters” What we found at an early stage was that efforts to find cases through testing those who had had contact with patients was not particularly effective. Further investigation revealed that while many patients do not infect anyone, some end up infecting many, thereby forming “clusters” of infected people from a single source. Therefore, in addition to contact tracing, we focused on a retrospective tracking of links between patients and found unrecognised cases surrounding the possible source, thereby identifying clusters. In addition, monitoring of the number of unlinked cases led to an early detection of exponential growth in the number of patients, which enabled the government to provide the public with an effective early warning. Clear and effective communications The government of Japan does not have the legal authority to implement strong measures such as lockdowns and curfews. Similarly, all the travel restrictions announced were voluntary requests. What the government was left with, therefore, was its capability to share knowledge about the disease with the public in an easy-to-understand manner. Through the cluster investigation, we recognised that the “three Cs” (closed, crowded spaces with close contact) were the major environmental risk factors that led to clusters. The government introduced the “Avoid three Cs” slogan from early March, which I believe helped significantly to delay the peak. Strong peer pressure Foreign visitors and expatriates in Japan can tell you how the Japanese are loyal to uncodified social norms. Physical distancing measures exist in Japan under the Special Measures Act, but the government can only encourage people to stay at home; closure of facilities can be requested, but offenders will not be punished. Yet the majority of people made efforts to stay at home and shopping centres remained closed in major cities during the state of emergency. Whether Japan can rely on the same methodology in a possible second wave remains to be seen. Bows and masks Social customs had a significant role to play. Shaking hands – let alone hugging and kissing – is seen as a western fashion to greet people. In addition, many Japanese are less reluctant to wear masks, as it is common to wear them in order to safeguard against pollen allergies in spring and flu in winter. Social customs such as these may have helped lower the transmission efficiency in the community – and may have made it easier for people to accept the new reality. It is reported that Anders Tegnell, chief epidemiologist of Sweden, who designed the soft-touch approach to the virus, remarked, “If we were to encounter the same illness with the same knowledge that we have today, I think our response would land somewhere in between what Sweden did and what the rest of the world has done.” Talking about the middle-approach, I cannot help wonder if Tegnell had these Japanese measures and customs in mind. Yet we cannot and should not let our guard down. Tokyo is now gradually reopening. Whether Japan can remain equally resilient and whether people can get used to a “new normal” by exercising peer pressure during the expected second wave remains to be seen. • Dr Tomoya Saito is director of the Department of Health Crisis Management at Japan’s National Institute of Public Health