A rapid, highly sensitive method to measure SARS-CoV-2 in wastewater
- Date:
- September 29, 2022
- Source:
- Hokkaido University
- Summary:
- A simple and economical method of detecting SARS-CoV-2 viral loads in wastewater with high sensitivity has been developed, expanding the use of wastewater-based epidemiology for tracking the virus in populations.
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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 multiple areas across the world to track the prevalence of the virus, serving as a proxy for determining the status of COVID-19. Of particular importance is 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., have developed a simple, rapid, highly sensitive method for the detection of SARS-CoV-2 in wastewater. The method, EPISENS-S, which does not require specialised 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, the viral loads in sewage have also been lower, and much more difficult to evaluate using established WBE methods -- due to their low sensitivity. Prior work by the research team showed that the SARS-CoV-2 virus was associated with solids in sewage, so they focused on developing a method to analyse the solid phase of wastewater.
The method they developed, EPISENS-S, involves centrifuging collected wastewater samples to separate all the solids in the samples. The solids were then treated with a commercially available kit to extract all the 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 treatment with polyethylene glycol followed by RNA extraction and reverse transcription to synthesize DNA: the method that is currently widely implemented in Japan. The 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 sewage treatment plants in Sapporo city, and found that there was a high correlation between changes in RNA concentrations in the collected samples and changes in the number of reported cases in the city. EPISENS-S can also detect and quantify the Pepper mild mottle virus (PMMoV), which is associated with fecal matter and is used as an internal control.
EPISENS-S provides a way to track COVID-19 cases that are asymptomatic, as well as those that have not been clinically confirmed. In addition, it has great potential to continue tracking the prevalence of SARS-CoV-2 as vaccination rates increase. Finally, EPISENS-S could also be adapted to track other viral diseases with low infection numbers and viral loads.
Story Source:
Materials provided by Hokkaido University. Note: Content may be edited for style and length.
Journal Reference:
- Hiroki Ando, Ryo Iwamoto, Hiroyuki Kobayashi, Satoshi Okabe, Masaaki Kitajima. 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 surveillance. Science of The Total Environment, 2022; 843: 157101 DOI: 10.1016/j.scitotenv.2022.157101
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