Wastewater-based epidemiology (WBE) has been shown to be an excellent means of understanding the spread of SARS-CoV-2 in communities. It is now used in various areas of the world to track the prevalence of the virus, and serves as a proxy for determining the status of COVID-19. It is particularly important that WBE can be used to estimate the prevalence of COVID-19, including asymptomatic cases. However, one of the major drawbacks of WBE for SARS-CoV-2 has been that the traditional method was not very sensitive and low viral loads could not be reliably detected.
A team of scientists from Hokkaido University and Shionogi & Co, Ltd. has developed a simple, rapid and highly sensitive method for the detection of SARS-CoV-2 in wastewater. The method, EPISENS-S, which requires no specialized equipment, was described in the journal Science of the Total Environment.
During the COVID-19 pandemic, Japan has had the lowest number of cases per capita. Thus, viral loads in wastewater have also been lower, and much more difficult to assess using established WBE methods-; due to its low sensitivity. The research team’s previous work showed that the SARS-CoV-2 virus was associated with solids in wastewater, so they focused on developing a method to analyze the solid phase of wastewater.
The method they developed, EPISENS-S, involves centrifuging the collected wastewater samples to separate all solids from the samples. Solids were then treated with a commercially available kit to extract total RNA; The RNA was then reverse transcribed and amplified to obtain a substantial amount of DNA copies. A separate set of samples was subjected to polyethylene glycol treatment followed by RNA extraction and reverse transcription to synthesize DNA—the method currently widely implemented in Japan. DNA obtained from each of these methods was subjected to quantitative PCR (qPCR).
The team found that the EPISENS-S method is approximately 100 times more sensitive than the polyethylene glycol method. They used EPISENS-S to conduct a long-term analysis of wastewater from two wastewater treatment plants in the city of Sapporo and found that there was a high correlation between changes in RNA concentrations to the samples collected and the changes in the number of cases reported in the city. EPISENS-S can also detect and quantify Pepper mild mottle virus (PMMoV), which is associated with fecal matter and used as an internal control.
EPISENS-S provides a way to track cases of COVID-19 that are asymptomatic as well as those that have not been clinically confirmed. In addition, it has great potential to continue to track the prevalence of SARS-CoV-2 as vaccination rates increase. Finally, EPISENS-S could also be adapted to monitor other viral diseases with low numbers of infections and viral loads.
Source:
Journal reference:
Ando, H., et al. (2022) The efficient and practical virus identification system with enhanced sensitivity for solids (EPISENS-S): a rapid and cost-effective SARS-CoV-2 RNA detection method for routine wastewater monitoring. Science of the total environment. doi.org/10.1016/j.scitotenv.2022.157101.