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A rendering of a virus

The novel coronavirus (SARS-CoV-2), which triggered a global pandemic in 2020, led to widespread infections and significant loss of life. A technology capable of precisely detecting and analyzing viruses in wastewater is gaining attention as a promising tool for monitoring the spread of various infectious diseases, including SARS-CoV-2. We spoke with KITAJIMA Masaaki, a leading young expert in this area of technological research.

KITAJIMA currently serves as Project Professor at the Research Center for Water Environment Technology of the School of Engineering at the University of Tokyo. In 2011, while a graduate student at the University of Tokyo, he received the 1st JSPS Ikushi Prize for his research titled “Molecular Epidemiological Analysis of Pathogenic Viruses in Water Environments and Control of Infection Risk,” which laid the foundation for his current field of study. (See the column for details about the JSPS Ikushi Prize.)

His research at the time focused on detecting gastroenteritis viruses, such as noroviruses. Specifically, it involved detecting viruses in aquatic environments, such as rivers and sewage inflows at wastewater treatment plants, and analyzing their genotypes. In his research, he utilized PCR,¹ which at the time was one of the most advanced technologies in the world.

“Viruses mutate as they repeatedly infect humans, in order to ensure their survival and reproduction. However, we found that the genotypes of viruses detected in people examined at medical facilities showed less diversity than the genotypes of viruses detected in wastewater and river water. In other words, viruses detected from such environmental waters indicated that there was a large number of people who carried the virus (were infected), either with or without symptoms, but who did not seek medical attention. Studying viruses in wastewater allows us to understand the actual scope of an infection’s spread, which may not be fully captured by medical facilities. This realization resulted in the current concept of wastewater surveillance,” explains KITAJIMA.

“Surveillance” in this context means monitoring, and the concept of wastewater surveillance (also known as wastewater-based epidemiology), as put forward by KITAJIMA, refers to the continuous monitoring and analysis of wastewater at fixed sites to identify and track trends in infectious diseases. When the COVID-19 infection began to spread, KITAJIMA realized that his research in the field could contribute to the response, and began working to detect and analyze SARS-CoV-2 in wastewater. Unlike previously detected viruses, however, SARS-CoV-2 is an enveloped virus, meaning it has a lipid membrane that helps it adhere to solids in wastewater. In addition, during the early stages of the outbreak, the viral load in wastewater was low. These factors made SARS-CoV-2 particularly difficult to detect. To overcome these challenges, KITAJIMA, in collaboration with a private pharmaceutical company, developed EPISENS^TM method, a technology with enhanced detection sensitivity capable of identifying viruses in wastewater even at low concentrations. This technology offers world-class sensitivity capable of detecting even a single new case of infection per 100,000 people per day. Using it, KITAJIMA was able to track changes in the viral load in wastewater, identify variants, and, in cooperation with local authorities and medical institutions, clarify the correlation between the actual number of reported patients and the concentrations of virus in wastewater.

Longitudinal monitoring of viral concentrations in wastewater using the EPISENS-M method at two wastewater treatment plants (WWTPs) in Sapporo City

[画像:Trends in virus detection in sewage in Sapporo City]

This figure shows the concentrations of SARS-CoV-2 detected in untreated wastewater in Sapporo City and the number of reported COVID-19 cases. A correlation is observed between higher viral concentrations and increases in the infection cases. The pepper mild mottle virus (PMMoV), shown in the upper half of the figure, is a plant pathogenic virus that infects hot and bell pepper species, causing mosaic-like mottling on the leaves and fruits. It is used as an indicator in wastewater surveillance because it is consistently present in measurable amounts in all wastewater.

“Wastewater surveillance offers four major benefits: it is efficient, objective, non-invasive/anonymous, and its results function as leading indicators. The last quality, in particular, is valuable for predicting future infectious disease outbreaks. Wastewater does not lie. Wastewater surveillance allows local authorities to issue early warnings and helps medical institutions formulate patient care plans,” explains KITAJIMA.

The EPISENS^TM technology, which is capable of detecting not only SARS-CoV-2, but also a variety of other pathogens, is expected to play a significant role in the field of border control measures to prevent the entry of viruses into Japan. Against this backdrop, there are high hopes for the wider adoption of wastewater surveillance.

JSPS Ikushi Prize
The JSPS Ikushi Prize was established to foster the development of young researchers by recognizing outstanding doctoral students who can be expected to contribute to the future advancement of academic research in Japan, thereby enhancing their motivation for study and research. On the 20th year of his ascending to the throne, Emperor Emeritus Akihito provided the endowment for this Prize to support and encourage young researchers who are diligently pursuing their studies and research within an economically challenging environment. This Prize was established in FY 2010 by the Japan Society for the Promotion of Science (JSPS).² For more information, see website JSPS Ikushi Prize.

• 1. Polymerase Chain Reaction. A technique based on the principle of amplifying deoxyribonucleic acid (DNA). It is used to detect viruses in samples.
• 2. Established in 1932 with an endowment from Emperor Showa, JSPS is today Japan’s only independent funding agency with a mission to advance science. JSPS carries out a wide variety of programs in pursuit of this mission. They include programs to fund scientific research, foster researchers, promote international scientific exchange, and reform university systems.

By FUKUDA Mitsuhiro
Photo: The Imperial Household Agency; PIXTA

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