First confirmed detection of the novel coronavirus in wastewater in Japan: How wastewater test could help track COVID-19
Last Updated 26 June, 2020. Cellspect Co., Ltd.
Recently, two research teams in Japan consecutively reported that the novel coronavirus (SARS-CoV-2) was first detected in the Japan’s wastewater [1,2] and similar findings had been reported in the Netherlands, the United States, France, Australia, Spain and other countries. The research team at the University of Toyama and the University of Kanazawa announced that it had succeeded in detecting the novel coronavirus in sewage water discharged from households by PCR, which was conducted once a week at four sewage treatment plants, one in Toyama Prefecture and three in Ishikawa Prefecture, between March 5 and April 24. If the amount of virus contained in the virus can be measured, it may be possible to grasp the infection situation and predict the sign of the second wave of infection at an early stage, the ministry said. The research group including Hokkaido University and Yamanashi University has also published a paper on the novel coronavirus in sewage. They said it may be able to use data from surveys of sewage to determine the prevalence of the new coronavirus. It is expected to be used as a judgment material for preventing the spread of infection and for resuming socioeconomic activities.
It has been reported increasingly over the world that the virus contained in the feces of infected persons is also detected in sewage, and it can be detected in the feces of asymptomatic persons. In a study on March 19th in The Lancet Gastroenterology & Hepatology, the researchers confirmed that the new coronavirus can appear in feces within three days of infection, which is much earlier than the time required for people to develop severe illness.  Another study shows that the median duration of SARS-CoV-2 in feces (22 days) was significantly longer than in respiratory (18 days; P = .002) and serum samples (16 days; P < .001).  Pathogens will eventually enter wastewater treatment facilities and therefore, wastewater testing, or wastewater-based epidemiology (WBE) is a potentially effective to understand the actual incidence of coronavirus disease 2019 (COVID-19) in a community, effective for early warning of COVID-19 outbreak.
The earliest report of COVID-19 in WBE was from the KWR Water Research Institute in the Netherlands. They discovered the RNA of the novel coronavirus at a sewage treatment plant in Amersfoort. At that time, no cases had been reported in this city. They believe that compared with testing on an individual basis, analysis of large-scale wastewater which is collected from more than 1 million people can better estimate the spread of new coronavirus. Because while health authorities focus only on those who are sick or with severe symptoms, wastewater testing can include people with mild or no symptom. This judgment was later actually verified. After they discovered the novel coronavirus RNA, the first local confirmed case was officially released. 
More than a dozen research groups worldwide followed this method and analyzed wastewater as a way to estimate the total number of infections in a community, helping track how and where disease is spreading. By analyzing the virus’ RNA in sewage, scientists may be able to identify the populations most at risk of infection—and most in need of lockdown—without painstakingly sampling every person, especially while individual tests remain in short supply.
From March 19, 2020 to May 1, researchers at Yale University in the United States also collected sewage sludge samples from a wastewater treatment plant in New Haven, Connecticut, which treats sewage from a population of about 200,000. They found that the RNA concentration of the novel coronavirus in sewage sludge was highly correlated with the epidemic curve and the number of hospitalizations in local medical institutions with a time difference (shown in the figure below). 
All of the above evidence shows that wastewater test can serve as a very easy and powerful tool. For decades, wastewater monitoring has been a weapon for virus tracking. In the past, polio vaccination was determined through wastewater monitoring, and this method was also used to detect antibiotic-resistant bacteria and illegal drugs.
However, proving that the RNA of this virus is detectable in wastewater samples is only an important first step. The bigger challenge is how to correlate the concentration of viral RNA in wastewater samples with the actual number of cases in the community. Researchers need to know how much virus can be excreted from the feces and to determine the amount of virus excreted by the human body through complicated calculation processes. Though more evidence is needed, these findings are still an encouraging proof of concept.
Akihiko Hata et al, June 12, 2020 “Detection of SARS-CoV-2 in wastewater in Japan by multiple molecular assays-implication for wastewater-based epidemiology (WBE)”. medRxiv
Eiji Haramoto et al., published online 2020 Jun 20. “First environmental surveillance for the presence of SARS-CoV-2 RNA in wastewater and river water in Japan”. Sci Total Environ. 2020 Oct 1; 737: 140405.
Yongjian Wu et al, published Online March 19, 2020 “Prolonged presence of SARS-CoV-2 viral RNA in faecal samples” Lancet Gastroenterol Hepatol. 2020 May;5(5):434-435.
Gertjan Medema et al, March 30, 2020 “Presence of SARS-Coronavirus-2 in sewage” medRxiv
Jordan Peccia et al, May 22, 2020. “SARS-CoV-2 RNA concentrations in primary municipal sewage sludge as a leading indicator of COVID-19 outbreak dynamics” medRxiv
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