SARS-CoV-2 virus in wastewater

T. G. Masaryk Water Research Institute together with the Research Institute of Veterinary Medicine in Brno, and with epidemiologists from the 1st Faculty of Medicine, Charles University, introduced a wastewater monitoring system in order to monitor the epidemic situation of the Covid-19 disease and predict its development. Monitoring is financed by the project VI04000017 "Use of wastewater monitoring as an early warning tool against the emergence of the epidemiological situation" programme 4. VS BV III. by institutional resources of the Ministry of the Environment through an internal TGM WRI grant 3600.52.33/2020. Sampling is performed by WWTP operators. The particular methodology was newly approved by the Ministry of Health of the Czech Republic.

What exactly do we monitor?

The principle of the system is the collection of untreated wastewater at selected wastewater treatment plants (WWTPs) suitable for the purpose, isolation of viral RNA, and quantitative detection of the number of the SARS-CoV-2 virus genomic units. Viral RNA is secreted into the wastewater by SARS-CoV-2 infected persons and therefore its amount correlates with their numbers in the areas connected to the monitored WWTPs. The results of the analyses show the good usability of the chosen method and thus the possibility of obtaining valuable objective epidemiological information at a disproportionately lower cost than with the help of clinical trials.

Where do we monitor?

The research team is currently performing continuous monitoring at four WWTPs in the Czech Republic and is analysing and evaluating the results of analyses of more than 550 samples taken at 66 WWTPs throughout the Czech Republic during all waves of the epidemic, and it is ready to offer cooperation to the healthcare sector for successful implementation of the European Commission recommendation on the introduction of systematic monitoring of SARS-CoV-2 in wastewater dated 17 March 2021. T.G. Masaryk Water Research Institute, p.r.i. ensures, independently or in cooperation with WWTP operators, wastewater sampling and, together with the Research Institute of Veterinary Medicine, p.r.i. in Brno, performs isolation and quantitative detection of SARS-CoV-2 RNA from wastewater in three laboratories.

What were the first results and what did they show?

Current results confirm that the system is able to detect the onset of a new wave of the epidemic before it is proven by clinical trials. Values from large treatment plants correlate very well, for example from both lines to the Prague WWTP, showing a rapid increase between weeks 35 and 41, and the Brno WWTP. At the Brno WWTP, there are currently higher values of viral RNA in wastewater than during the peak epidemic in spring and autumn, which may mean, for example, higher numbers of asymptomatic individuals secreting viruses into wastewater or higher viral load in current virus variants. Wastewater monitoring shows that it is a very good objective tool for monitoring the development of the virus in a population that does not require testing of individuals.

And what the fresh results show?

Commentary on the latest results (updated to May 16, 2022):

The current situation suggests that in the Czech Republic, the current variant of coronavirus SARS-CoV-2 is still present at a level approximately corresponding to the end of 2021, but it no longer causes a significant epidemic or health risk for the majority of the population.

  • Prague WWTP – the autumn wave of the epidemic was very well captured at SVL (existing) and NVL (new water line). The data on the concentration of viral particles in wastewater before the end of 2021 indicates another emerging wave, which was confirmed by the numbers of positively tested persons. The current situation, as with Moravian WWTPs, suggests that there may be more infected people in the population than are detected by clinical trials. The concentration of virus particles in Prague’s wastewater fluctuates in February and March. A complete decline in the virus in the population cannot be confirmed.
  • Kladno WWTP – wastewater monitoring captured the autumn and February waves of the epidemic very well. Current data from wastewater show a low virus content in correlation with a low number of people with a positive test.
  • Brno WWTP – wastewater monitoring reliably captured the autumn wave and, after a decline at the end of 2021, showed the onset of another wave in January 2022 in correlation with the numbers of positively tested persons. From mid-February to mid-April, fluctuating but relatively stable levels of viral RNA were detected in the wastewater, which was accompanied by a decrease in the number of positive persons tested. Current data from the end of April and the beginning of May show a decrease in the level of wastewater exposure to viruses, accompanied by a gradual reduction in the number of people tested positive. The level of wastewater loading shows, compared to the previous period, the numbers of people shedding viruses into the wastewater at the level of December 2021.
  • Břeclav WWTP – wastewater from this WWTP has captured all previous waves of the epidemic. Data from 2022 show fluctuating but relatively stable levels of viral RNA in wastewater. The latest data from April and May 2022 confirm the presence of a higher number of people shedding virus fragments into wastewater compared to the declining trend in the number of people tested positive.

In the middle of March 2022, the numbers of positively tested persons were corrected last time for verified data from the ISIN system (SZÚ) in the charts, therefore they may differ from the previously presented ones. At present, the current numbers for individual cities are no longer freely available. The numbers of positive persons for the last 14 days available on the website https://obce.nery.cz/ (in Czech) were used in the charts. Public data are often affected by error and do not include population numbers in connected municipalities.

Fluctuations in the capture of RNA sought in wastewater can be caused by:

a) different amount of wastewater = different dilution of the amount of viral RNA fragments present,
b) by taking in another weekly regime (weekend),
c) inhomogeneity of the collected sample (waste water contains a number of other substances and particles, sampling is performed after mechanical removal of coarse impurities),
d) the volatile ratio of industrial and municipal wastewater.

You can learn more about the issue of coronavirus in surface and wastewater, and the possibilities of using the results as a diagnostic medium, in the articles of the VTEI journal here (in Czech) and here (in Czech). A Czech television (in Czech) report from Hana Sovová and an article on Seznam News (in Czech) server from Hana Zvěřinová Mlejnková also deal with the topic.