Wow! Cool Laboratory [Researcher Introduction]

Masaaki Kitajima
Faculty of Engineering,
Division of Environmental Engineering,
Research Group of Environmental Engineering,
Water Quality Control Engineering Laboratory
Assistant Professor
Masaaki Kitajima
[Profile]
Field of research: water environment technology, environmental virology, civil environmental systems
Research theme: wastewater-based epidemiology of COVID-19, health-related water microbiology
E-mail: mkitajima[a]eng.hokudai.ac.jp
2021.01.18

Understanding the actual infection prevalence by detecting viruses in wastewater
“Wastewater-based epidemiology” enhances the value of wastewater system as a social infrastructure

Wastewater-based epidemiology is useful for understanding the infection prevalence of COVID-19

COVID-19 (coronavirus disease 2019) was first reported in Wuhan, China at the end of 2019 and spread worldwide. The disease mainly transmits via droplets and human-to-human contacts, and respiratory organs, such as the respiratory tract and lungs, are considered to be the major sites of infection. PCR tests (RT-qPCR) are generally performed at health centers and other facilities to confirm infection, but it is difficult to accurately understand the total number of patients and the increasing/decreasing tendency of infection because some patients have mild or no symptoms.

Under these circumstances, Assistant Professor Masaaki Kitajima of the Water Quality Control Engineering Laboratory is working on the development of a technology to understand the prevalence of COVID-19 from the perspective of “wastewater-based epidemiology.”
Assistant Professor Kitajima specializes in environmental virology and water environment technology. Wastewater-based epidemiology is a research field where markers including viruses in wastewater are detected to estimate the epidemic situation and evaluate the health status of people from the data.

“Researchers in the field of water virology, including myself, have mainly focused on enteric viruses, such as norovirus and poliovirus. Initially, since the novel coronavirus (SARS-CoV-2) is a respiratory virus, we, researchers in the field of water virology, did not think that we could contribute to infection control. However, it was reported that the virus was detected in the feces of infected people in the early stage of the epidemic. With that, we thought that it might be possible to detect the virus in wastewater and so we initiated this research.”

In April 2020, Assistant Professor Kitajima published the world’s first review article on SARS-CoV-2 in wastewater in collaboration with overseas researchers. After that, as a member of the international collaborative research group, he detected SARS-CoV-2 RNA in wastewater samples from Brisbane, Australia and Louisiana, USA. In Japan, in collaboration with the University of Yamanashi, he published the first paper reporting the detection of SARS-CoV-2 RNA (Note 1).

“In the control of norovirus and poliovirus infections, the results of wastewater surveys have been used as a basis for determining the effectiveness of public health intervention. Regarding COVID-19, wastewater-based epidemiology is also considered to be useful for understanding the actual infection prevalence.”

Aiming to establish a concentration method that makes it possible to detect the virus

Since the concentration of viruses in sewerage is diluted with wastewater and stormwater, a concentration technique is required to increase the concentration of the virus to a detectable level. Enteric viruses, such as norovirus, have a viral particle structure in which genetic materials (DNA or RNA) are protected with a protein called capsid. In SARS-CoV-2, however, the outmost layer of the virus particles is an envelope (a membrane consisting of lipids and glycoproteins), and it is difficult to efficiently concentrate the virus using the method employed for enteric viruses.

“We evaluated virus recovery efficiencies of multiple concentration methods and performed comparative measurements toward establishment of a standard method for SARS-CoV-2 detection in wastewater (Note 2).”
The results are considered to be widely referred to in selecting a method for concentrating SARS-CoV-2 in wastewater, and they are expected to contribute greatly to the establishment of a standard detection method.

Developing social infrastructure to prepare for the next pandemic

Great expectations are being placed by society on the data from wastewater-based epidemiological studies as one of the criteria for making policy decisions regarding infectious disease control and as a tool for understanding the actual state of epidemics in the future. In the world, an international research project on wastewater-based epidemiology of COVID-19 is currently underway, and researchers from 13 countries, including Assistant Professor Kitajima, participate in this project. In the future, it is expected that wastewater-based epidemiology will progress through international collaboration.

With the progress of research and study, what we should focus on in the future is the social implementation of wastewater-based epidemiology. Although water and wastewater systems in Japan are well constructed, there are few wastewater treatment plants equipped with facilities that can detect and monitor viruses.

Assistant Professor Kitajima says, “I think it will be important to promote wastewater-based epidemiology in the future. In addition to eliminating wastewater and rainwater in cities, routine monitoring of wastewater helps to identify novel viruses and detect the outbreak of new infectious diseases early. I think that the role as a social infrastructure will be greatly developed by adding new values and functions of noticing signs of infection and providing information for making decisions on public health intervention at an early stage. The spread of wastewater-based epidemiology and the development of social infrastructure should be important measures to prepare for the next pandemic.”

Industry-academia-government efforts for the social implementation of wastewater-based epidemiology have also begun. Assistant Professor Kitajima has been participating in the projects under the Ministry of Land, Infrastructure, Transport and Tourism and the Ministry of Health, Labour and Welfare, and has started collaborative research with a major pharmaceutical company, and plans to promote the construction of a wastewater monitoring system, technical development for virus genetic information analysis, and the establishment of a research and inspection system.

Note 1. Japan’s first environmental surveillance on the presence of SARS-CoV-2 RNA in wastewater and river water
From March 17 to May 7, 2020, a total of 13 water samples were collected in Yamanashi Prefecture, including five samples each of influent wastewater at a wastewater treatment plant (treatment method: conventional activated sludge method) and treated wastewater before chlorination (final sedimentation tank effluent), as well as three samples of river water (at points sufficiently far from the wastewater treatment plant). Two types of virus concentration methods and six types of PCR methods were combined in order to detect SARS-CoV-2 RNA in the water samples. As a result, SARS-CoV-2 was detected at a concentration of 2,400 gene copies per liter in one sample of treated wastewater before chlorination collected on April 14.
Note 2. Evaluation of the recovery efficiency of coronavirus in wastewater for each method
Murine hepatitis virus (MHV) was spiked into untreated wastewater, and MHV in wastewater was concentrated using seven types of virus concentration methods. The recovery efficiency of MHV by each concentration method was determined.