Roles of Public Health Centers and Cluster-Based Approach for COVID-19 Response in Japan

Global spread of coronavirus disease 2019 (COVID-19), which was first identified in China in December 2019, rapidly progressed to a pandemic.^1,2 In Japan, the first COVID-19 case was identified on January 15, 2020.³ Distribution of COVID-19 cases were initially limited to the major cities, however, the disease gradually spread to smaller cities. As of November 30, 2020, more than 146,000 COVID-19 cases, including over 2,100 deaths, had been reported nationwide.⁴

During the first wave of the COVID-19 pandemic, the Ministry of Health, Labour and Welfare (MHLW) and the National Task Force for COVID-19 Outbreak in Japan, implemented a cluster-based approach strategy.⁵ The concept of this strategy was to conduct an intensive retrospective investigation on the clusters of COVID-19 cases, so that we could identify the source and the specific environmental settings in which COVID-19 superspreading events (ie, clusters) were more likely to occur and suppress the transmissions by restricting those settings and urging behavioral changes to the general public. In the nationwide response to COVID-19, the public health centers (PHCs) spearheaded in the response in the local communities.

As of 2020, there are total of 469 PHCs in Japan, including 355 prefectural centers, 91 city centers, and 23 specified district centers of Tokyo Metropolitan.⁶ Over 28,000 officers are stationed in PHCs, containing substantial number of public health specialists, such as public health doctors (n = 728), public health nurses (n = 8,327), pharmacists (n = 2,904), and laboratory technologists (n = 746).⁷ Duties of PHCs are specified by the Community Health Act,⁸ which covers various health-related areas, including maternal health, mental health, food safety, and infectious diseases. Infectious disease-related duties include the first response to the potential outbreaks in their jurisdictions. During the COVID-19 outbreak, PHCs took part in a wide range of public health activities, including surveillance, case investigations, distribution of medical equipment, health monitoring of contacts, and coordinating clinical sampling in outpatient centers and testing in public health institutes.

When new COVID-19 cases were identified in the jurisdictions, PHCs retrospectively searched for potential COVID-19 cases among individuals who had contact with the confirmed cases within the past 14 days. This was intended to identify source cases and superspreading events/clusters in which new COVID-19 cases were presumed to have acquired infections. When clusters were identified, individuals who could have been exposed to COVID-19 in those clusters were investigated and requested to self-quarantine. They were monitored for any signs of symptoms for 14 days after the exposure and were subjected to COVID-19 testing when they developed symptoms or when they were strongly suspected of having COVID-19.⁹ In fact, vigorous case investigations and following COVID-19 testing revealed the source patients or clusters of over 60% of the confirmed COVID-19 cases, which supported the implementation of the cluster-based approach at the community level.¹⁰

Several factors were assumed to have contributed to the successful implementation of the cluster-based approach in PHCs, among which the biggest factor could have been the rapid reinforcement of the human resources for the community engagement. During the COVID-19 pandemic, many countries, including Japan, have faced a challenge of the insufficient human resources for implementing a large-scale case investigation and contract tracing in the community. In Japan, PHCs tackled this challenge by reassigning public health officers of the prefectural administrative offices to PHCs, reemploying former PHC officers, and newly recruiting public health specialists from outside PHCs.¹¹ While some countries were recruiting contact tracers irrespective of their academic backgrounds, PHCs in Japan utilized only public health experts for case investigations and contract tracing. For example, public health nurses, comprising nearly 30% of the public health officers in Japan, are registered nurses with additional field training for public health nursing from universities and postgraduate schools.¹² Public health nurses who had been on leave underwent trainings on subjects such as infection prevention and control measures, case investigation, and contact tracing before reassignment.¹³

According to the nationwide cross-sectional survey conducted by the MHLW COVID-19 Response Headquarters on May 11, 2020, 72% (n = 92) of the 127 PHCs conducted reassignment of public health officers from the prefectural administrative offices, and 70% (n = 89) of the PHCs reemployed former PHC officers to enhance their COVID-19 response capacities.¹² Reassignment of public health officers was undertaken even across the prefecture borders upon the surge of COVID-19 cases in some local government areas.¹⁴ In PHCs with many cases in their jurisdictions, those efforts led to a significantly increased number of public health officers; approximately 3.8 more (from 256 to 964) than usual, according to a survey on surge capacity of PHCs in the epidemic area.¹² In addition, 23% (n = 29) of the 127 PHCs newly recruited public health specialists from outside PHCs, such as universities and medical facilities in the region.¹² Public health specialists from universities and medical facilities supported various public health activities, including case investigations, contact tracing, and data management, depending on their expertise.

The COVID-19 pandemic has highlighted the significant role public health specialists outside PHCs play in enhancing the capacities of PHCs to respond to public health emergencies with emerging infectious diseases. Moreover, the current pandemic has highlighted the importance of building trust between PHCs and public health specialists outside PHCs during the nonpandemic period. On June 19, 2020, notifications were made by the MHLW to strengthen the capacities of the PHCs in data management, polymerase chain reaction testing, case investigations, distribution of resources in medical facilities, and health monitoring of the residents.¹⁵

Based on these lessons learned in the current pandemic, further efforts to enhance the preparedness of PHCs for the potential resurge of COVID-19 cases—eg, recruiting public health officers, increasing capacities to utilize digitalized systems, and generating contingency plans for outsourcing private sectors—are in progress. Meanwhile, the shortages of infectious disease specialists who give guidance in management of infectious disease-related public health emergencies in the local governments, such as field epidemiologists and specialists for risk assessment, has been pointed out by the evaluation of the World Health Organization; this has become an important issue in the current COVID-19 pandemic.^16,17 In parallel with the enhancement of PHC capacities, the strengthening of human resources specializing in the management of infectious disease-related emergencies is an urgent matter in Japan.

In addition to the rapid reinforcement of the human resources, the successful implementation of the cluster-based approach in the community was also supported by the prompt appreciation of its core concept—the enhanced retrospective contact tracing—by the public health officers in PHCs. PHC officers in Japan are familiar with retrospective contact tracing through their experience in outbreak investigations for tuberculosis (TB). TB is still a major public health issue in Japan, with over 15,000 newly identified cases each year.¹⁸ When a new TB patient is identified, public health officers in PHCs undertake a contact investigation in the communities. The contact investigation for TB includes a component of finding the source patients and collecting information about the social settings where the transmission might have occurred.¹⁹ This component aims to not only find the source patients and lead them to proper treatment, but also, more importantly, to collect data on the transmission patterns in the community to establish better preventive measures for the identified pathways.

It is noteworthy to mention that a component of retrospective contact tracing is a unique strategy compared to those adopted in other countries. For example, the US Centers for Disease Control and Prevention (CDC) does not recommend source case investigation using retrospective approach, unless the index case is a child younger than 5 years of age.²⁰ The CDC's strategy for omitting the retrospective component for TB patients is based on the low cost-effectiveness of the source case investigations, due to the low transmission rate of the patients with active TB infections. Other factors, such as the prevalence of TB in the region and the distribution of public health resources are also attributing to the selection of contact investigation strategies; therefore, the validity of the retrospective contact tracing for TB is not discussed in this article. However, it might be possible that such accumulated experiences of retrospective contact tracing in TB response have resulted in the prompt appreciation and administration of the cluster-based approach in Japan by PHC officers in the current COVID-19 outbreak.

Conclusion

Rapid reinforcement of human resources and accumulated experiences of retrospective contact tracing might have contributed to the successful implementation of the cluster-based approach at the community levels. The surge capacity of PHCs in the current COVID-19 outbreak highlighted the importance of better preparedness in the local public health sectors during the nonpandemic period. Further reviews on the preparedness of PHCs are warranted to strengthen their capacities in response to future infectious disease-related public health emergencies.

Acknowledgments

This work was supported by MHLW Health, Labour and Welfare Policy, Research Grants Program Grant Number JPMH20HA2007.