PHWR Public Health Weekly Report

The coronavirus disease 2019 (COVID-19) pandemic, which began in China in December 2019, resulted in several confirmed COVID-19 cases and deaths worldwide. In the Repubilc of Korea (ROK), COVID-19 was designated as a first-class notifiable infectious disease from January 20, 2020, when the first confirmed case of COVID-19 was reported, to April 24, 2022. Since then, it has been designated as a second-class notifiable infectious disease subject to comprehensive monitoring [1]. With the COVID-19 pandemic, wastewater-based surveillance, which can preemptively help in monitoring and providing response to outbreaks of infectious diseases in communities, has received attention in many countries, including the United States, Europe, and Japan, and has been actively used in national infectious disease surveillance policies [2]. The ROK is also focusing on the promotion and management of wastewater-based surveillance, including the 2-2-4 [Establishment of wastewater-based infectious disease surveillance system] among the national tasks of the Korea Disease Control and Prevention Agency (KDCA) [Advancement of Infectious Disease Response System] [3]. On April 15, 2022, the KDCA introduced a wastewater-based infectious disease surveillance system and established a step-by-step expansion plan with the goal of nationwide operation to recognize the occurrence of infectious diseases in communities as one of the measures for "strengthening of the monitoring system for new variants and re-emergence" among the post-omicron response plans [1]. The goals of this system also include the establishment of a wastewater-based infectious disease monitoring system in the 3rd (2023–2027) Master Plan for Prevention and Management of Infectious Diseases.

Accordingly, the KDCA conducted a pilot study on the effectiveness of wastewater-based infectious disease surveillance applied domestically since 2021. Based on this, in 2023, the KOrea WAstewater Surveillance (KOWAS) project is being carried out in collaboration with 17 cities or provinces and 18 Institute of Health and Environment Researches nationwide. Through this policy report, we introduce the KOWAS conducted by the KDCA and discuss the directions for future development of such surveillance systems.

1. Definition of an Infectious Disease Surveillance System

“Infectious disease surveillance” refers to the process of systematically and continuously collecting, analyzing, and interpreting data related to the occurrence of infectious diseases and the pathogens and vectors of infectious diseases and distributing the results in a timely manner for the prevention and management of infectious diseases [Infectious Disease Control and Prevention Act, Article 2, Subparagraph 16]. Surveillance systems are divided into mandatory, sentinel, and supplementary surveillance systems. In mandatory surveillance systems, all doctors, dentists, doctor of Korean medicine heads of medical institutions, unit commanders (military surgeons), and heads of infectious disease pathogen identification institutions must report as per Article 11 of the Infectious Disease Control and Prevention Act. In sentinel surveillance systems, an infectious disease specimen surveillance institution is designated as per Article 16 of the Infectious Disease Control and Prevention Act, and the system operates only after receiving a report from the designated institution. The supplementary surveillance system supplements the infectious disease surveillance system and actively and promptly responds to infectious diseases that are not notifiable as infectious diseases but require monitoring of occurrence and trends [4]. Wastewater-based infectious disease surveillance, which was recently established in the Infectious Disease Control Project Guidelines in 2023 and supervised by the KDCA, is a new method that can complement the existing surveillance system.

2. Background of National Wastewater-based Infectious Disease Surveillance

Research on wastewater-based monitoring has been steadily conducted overseas, and it involves the screening of pathogens and health indicators by analyzing wastewater samples. The primary objectives include monitoring and surveillance of 1) illegal drugs and narcotics, 2) infectious pathogens and bacteria, 3) population markers, 4) industrial chemical exposure markers, and 5) factors such as stress, food, diet markers, or biological markers [5]. Starting with the COVID-19 pandemic in December 2019, wastewater-based surveillance technology is increasingly being used in other countries to track and manage symptomatic and asymptomatic infections as an auxiliary means to clinical surveillance, which only identifies symptomatic infected individuals [6]. In early 2020, after reporting that the genetic signal of COVID-19 increased with the number of confirmed COVID-19 cases in the inflowing wastewater of six wastewater treatment plants in the Netherlands and Australia, other countries worldwide have paid attention to wastewater-based surveillance systems [7].

The United States Department of Health and Human Services and the United States Centers for Disease Control and Prevention formed the National Sewage Surveillance Interagency Leadership Committee (NSSIL). Through the NSSIL, member organizations support policy decisions by developing and implementing the National Wastewater Surveillance System to collect, analyze, and integrate data on COVID-19 cases [8]. By February 2023, > 1,300 sewage treatment plants across the United States have been conducting COVID-19 surveillance [9]. The World Health Organization also announced wastewater-based COVID-19 surveillance guidelines (April 2022) as part of the COVID-19 environmental monitoring policies and based on the 14th International Health Regulations meeting, which recommends “sewage monitoring” (January 30, 2023) with a declaration of COVID-19 as public health emergency (Public Health Emergency of International Concern) [10,11].

The advantages of monitoring infectious diseases using wastewater are as follows. 1) In the monitoring of patients, such as COVID-19 patients, it is possible to detect viruses excreted 6–8 days earlier than that noted in clinical samples, regardless of the presence or absence of symptoms. 2) Monitoring of patients is possible without invasion of privacy. 3) Periodic monitoring according to time and region is possible. 4) Involve more significant budget savings than clinical surveillance for prior monitoring. 5) It is possible to monitor various pathogens related to public health other than COVID-19 in wastewater samples, such as virus variants, antibiotic-resistant bacteria, and waterborne pathogens. The wastewater-based infectious disease surveillance system enables periodic monitoring within the region without invading individual privacy for early detection of new emerging infectious pathogens [12]. Therefore, establishment of a nationwide wastewater-based infectious disease surveillance system combined with existing clinical surveillance can serve as a basis for responding to new infectious diseases through efficient surveillance of infectious diseases in communities (Figure 1).

Figure 1. The Wastewater Surveillance System in the Republic of Korea

3. Results of Pilot Project on National Wastewater-based Infectious Disease Monitoring

Wastewater-based infectious disease surveillance can be divided into community wastewater-based and building-level wastewater-based surveillance. Community wastewater-based surveillance monitors temporal trends in virus transmission through community-level wastewater monitoring based on sewage treatment plants. However, the spatial trends cannot be explained because sewage from different sources is diluted or mixed. Moreover, since building-level wastewater-based surveillance targets specific buildings, such as schools, prisons, and hospitals, it can serve as a basis for target-specific interventions (such as expansion of inspections, wearing masks, and social distancing) when potential infection hotspots are discovered [13].

Since 2021, the KDCA has conducted a pilot project to establish a wastewater dynamics-based infectious disease monitoring system in Sejong for sewage monitoring in the community through the funding of policy research—"Study on how to introduce an infectious disease surveillance system using wastewater” (PI: Seong-Pyo Kim, Professor at Korea University). This project involved the monitoring of 32 infectious diseases in a total of 66 sewage samples collected from sewage treatment plants, educational institutions, multi-use facilities, and medical institutions in Sejong and resulted in the detection of a total of 11 pathogens, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In addition, a similar trend was observed between the infectious pathogens analyzed in sewage samples and the number of reported cases based on clinical diagnosis, confirming the potential of monitoring infectious diseases through sewage-based surveillance systems. In addition, for wastewater-based monitoring at building levels, periodic monitoring of wastewater-based SARS-CoV-2 was conducted at long-term care hospitals and nursing homes in Sejong. Based on this, a study is ongoing to explore a significant relationship between the pathogens analyzed in wastewater samples and the number of reported cases based on clinical diagnosis. Research findings have confirmed the usefulness of wastewater-based infectious disease monitoring in the ROK. To establish a wastewater-based monitoring system suitable for each region and to integrate nationwide wastewater monitoring results, quality control of wastewater monitoring experimental techniques was implemented through the 2022 policy research project—"Establishment of an infectious disease surveillance system using local-based wastewater.” Thus, a wastewater-based infectious disease surveillance system was introduced by 18 Institute of Health and Environment Researches in 17 cities or provinces nationwide, providing a foundation for sewage monitoring operations according to each region.

4. Operation Status of National Wastewater-based Infectious Disease Surveillance Project

The KDCA is working on “Establishment of a New Epidemiological Surveillance System (Wastewater Surveillance)” as a government subsidy project in 2023. For smooth implementation of the nationwide KOWAS (KOrea WAstewater Surveillance) project, the 2023 Infectious Disease Control Project Guidelines established by the KDCA newly included KOWAS. The goal of this project is to establish a monitoring system for the incidence and trend of major infectious diseases in wastewater in communities through regional wastewater-based infectious disease monitoring. The project also aimed to periodically monitor infectious pathogens in wastewater samples in wastewater treatment plants in different regions in the ROK, jointly with the KDCA as well as city or provincial Institute of Health and Environment Research (18 locations nationwide). The roles of each participating organization are as follows: 1) The KDCA: establishment of business plans; securing and issuing of budget; collection of monitoring results; preparation of weekly monitoring reports; provision of laboratory-related technical support and quality control; improvement in inspection methods; discovery of monitoring targets by region; and promotion of specialized projects; 2) City or Provincial Institute of Health and Environment Research: selection of wastewater treatment plants and pathogens to be monitored; analysis of pathogens in wastewater; and reporting of results; 3) Ministry of Environment: implementation of projects on wastewater samples in wastewater treatment plants (Table 1).

Table 1 The participating institutions of KOWAS project in 2023

Institute of Health and Environment Research	Number of institution	Number of wastewater treatment plant
Overall	18	64
Seoul	1	5
Busan	1	3
Daegu	1	2
Incheon	1	5
Gwangju	1	3
Daejeon	1	2
Ulsan	1	4
Sejong	1	3
Gyonggi	1	1
Gyonggi Northern Office	1	1
Gangwon	1	3
Chungbuk	1	5
Chungnam	1	1
Jeonbuk	1	2
Jeonnam	1	8
Gyeongbuk	1	5
Gyeongnam	1	3
Jeju	1	8

KOWAS=KOrea WAstewater Surveillance..

Pathogens that must be included in wastewater monitoring are SARS-CoV-2, norovirus, human influenza virus (A/B), and antibiotic-resistant bacteria (2nd half of 2023). Other pathogens, such as hepatitis A virus, acute respiratory virus, and intestinal bacteria, may be included depending on the situation of each local government. In addition, when a new foreign infectious disease is introduced into the ROK, it is possible to preemptively prepare the basis for surveillance of the imported infectious diseases by adding them as pathogens subject to monitoring in wastewater. There are 64 sewage treatment plants subject to monitoring in 2023, and monitoring results are reported to the KDCA at least once a week in each region (Table 2, Figure 2).

Figure 2. Wastewater treatment plants participating in KOWAS
KOWAS=KOrea WAstewater Surveillance.

Table 2 The examine pathogens of KOWAS project in 2023

Category	Pathogens
Essential	SARS-CoV-2
	Norovirus
	Human influenza virus (A/B)
	Antibiotic-resistant bacteria (Aug. 2023–)

Pathogens to be monitored can be added (infectious diseases imported from abroad, etc.)..

KOWAS=KOrea WAstewater Surveillance..

5. Plan and Direction for Development of National Wastewater-based Infectious Disease Surveillance

The KDCA is conducting a wastewater-based national infectious disease surveillance project based on wastewater treatment plants in communities. This is a measure to improve the new infectious disease crisis response system, strengthen community capacity, and map out active preparation and response plans for infectious disease crises and environmental changes. Antibiotic-resistant bacteria, in addition to the three targeted pathogens (SARS-CoV-2, norovirus, and human influenza virus (A/B)), will be subjected to essential wastewater monitoring. Moreover, a wastewater sample transport system will be established to facilitate the wastewater-based infectious disease surveillance project. Based on this, a standard operating procedure will be developed for transporting wastewater samples to wastewater treatment plants, and participating organizations will be managed and supported. Similarly, in the Netherlands, local governments operate a nationwide wastewater-based infectious disease surveillance network. Samples are received from approximately 300 sewage treatment facilities and analyzed for SARS-CoV-2 at least three times a week, and the results are publicly disclosed on the Dutch government's coronavirus dashboard [14]. The KDCA plans to establish a web page for visualizing geographic information by region through periodic collection and publishing of sewage monitoring results by Institute of Health and Environment Research. As a mid-to-long-term plan, wastewater-based infectious disease surveillance at airports and ports in cooperation with relevant departments and institutions for early recognition of infectious diseases imported by travelers from overseas will be promoted. In addition, some cities or provinces plan to conduct wastewater monitoring at building levels as a pilot plan for facilities with a high risk of outbreaks of infectious diseases, such as hospitals, nursing homes, schools, and correctional facilities. In addition, the target areas and pathogens will be gradually expanded for wastewater monitoring within communities. A preemptive monitoring system operation plan is being established by adding monitoring targets when a new infectious disease is introduced into the country.

As one of the limitations of sewage-based infectious disease monitoring conducted overseas, the experimental results vary depending on the characteristics of the sewage, which are influenced by contamination and dilution caused by surface water inflow. The results of the surveillance of sewage-based infectious diseases are used as an auxiliary tool for clinical diagnosis techniques. The KDCA aims to facilitate effective monitoring and comparison of sewage monitoring results by region through the introduction of concentration and extraction experiment equipment specialized in sewage sample analysis to Institute of Health and Environment Research. This is to improve analysis efficiency, through a reduction in sewage sample processing time, and facilitate large-capacity polymerase chain reaction analysis and standardized experimental methods. The KDCA plans to continuously secure related budgets for this purpose. In addition, we will continue to develop national wastewater-based monitoring projects to monitor infectious diseases within communities and preemptively monitor infectious diseases imported from abroad through wastewater in specific group facilities (such as hospitals, nursing homes, schools, and correctional facilities), airports, and harbor, with regular cooperation with 18 Institute of Health and Environment Researches nationwide.

Wastewater-based infectious disease surveillance is a new infectious disease surveillance system that can compensate for various limitations of the existing clinical surveillance system, such as difficulties in preemptive monitoring of asymptomatic patients, concerns about personal information leakage, and huge budgets. This surveillance approach is actively being used as a strategy to respond to post-omicron effects worldwide, including the United States, the United Kingdom, and Japan. In the ROK, related policies are being promoted in line with this trend. The KDCA has conducted a wastewater-based infectious disease surveillance project since 2021. Through the government-subsidized project in 2023—Establishment of a New Epidemiological Surveillance System (Wastewater Surveillance), the KOWAS project for 17 cities or provinces in different provinces nationwide is being conducted in collaboration with 18 Institute of Health and Environment Researches, sewage treatment plants, and related ministries. The KOWAS project plans to lay the foundation for surveillance to prepare for and respond to national infectious disease crises through continuous development and advancement of experimental techniques.

Ethics Statement: Not applicable.

Funding Source: None.

Acknowledgments: Thanks to department related to the Institute of Health & Environment Research, which is participating in the KOWAS project, and Ministry of Environment and Wastewater Treatment Plants for their cooperation in collecting sewage samples.

Conflict of Interest: The authors have no conflicts of interest to declare.

Author Contributions: Conceptualization: JJ. Visualization: JJ. Writing – original draft: JJ, SYP, AK, YJC. Administrative support: SHK, AK. Writing – review & editing: SSK, SL, DK.