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.

Course of the coronavirus epidemic in municipal wastewater?

The obtained results confirmed that the system is able to detect the onset of a new wave of the epidemic before it is proven by clinical tests. Ongoing regular monitoring of SARS-CoV-2 virus RNA in wastewater in 4 cities of the Czech Republic (Prague, Brno, Kladno, and Břeclav) at 5 WWTPs (Prague WWTP – the existing and the new water line, Brno WWTP, Vrapice-Kladno WWTP, and Břeclav WWTP) is a unique tool that allows capturing the current state of the occurrence of the coronavirus in the Czech Republic and the expected onset of the next epidemic wave. Wastewater monitoring is thus a functioning objective tool for monitoring the development of the virus in the population, which does not require testing of individuals.

The RNA monitoring of the SARS-CoV-2 coronavirus in wastewater, carried out since April 2020, captured the individual waves of the covid-19 epidemic in the Czech Republic and can thus be considered a functioning marker of the occurrence of covid-19 in the population.

Objective data obtained from wastewater monitoring show that the almost complete elimination of the virus in summer 2021 was followed by a sequence of waves of increased occurrence of GE (genome units) of the SARS-CoV-2 virus in wastewater, correlated with the number of persons tested positive for covid-19, detected by PCR tests.

The ratio of the viral load of wastewater to the number of positive tests changed at the beginning of summer 2022, i.e. the virus was present in the population, but did not significantly affect the health of the population.

Based on the progress so far, it can be assumed that in the population of the Czech Republic there will be alternating waves of increased occurrence of the virus in the population without a significant effect on public health and their gradual stabilization at the level of the occurrence of common infectious diseases with the probability of the onset of an epidemic only in the case of a new variant of the virus.

Two-year wastewater monitoring showed the adaptation of the population of the Czech Republic to the presence of the SARS-CoV-2 virus.

And what the fresh results show (updated to Jan 16, 2023)?

The amount of SARS-CoV-2 RNA in wastewater in December oscillated at the level of tens to hundreds of GE/1ml at smaller WWTPs (Břeclav, Kladno) and hundreds at WWTPs of large cities (Prague, Brno), i.e. at a lower level than in the autumn months. Compared to the previous waves of the epidemic, the real incidence of the virus in the population corresponded to orders of magnitude higher numbers of infected people than the clinical tests showed.

Control samples taken on January 10, 2023 at the Brno and Břeclav WWTPs showed a significant decrease in the amount of the covid-19 marker in the wastewater. The number of people tested positive also decreased. Wastewater confirms that the current epidemic of respiratory diseases is not caused by covid-19.

Monitoring in the Czech Republic ended with the end of the COVMON 2021–2022 project and the internal VÚV grant for 2022 at the end of December 2022. Current data on the objective occurrence of covid-19, based on the amount of its specific marker in wastewater, can only be obtained from data from other European countries in which wastewater monitoring continues. Links can be found here.

The results of wastewater monitoring in the above graphs are compared with the verified numbers of positively tested persons, from the ISIN system, continuously processed by the Department of Biostatistics of the SZÚ for specific monitored locations. Data on weekly numbers of positively tested individuals in the Czech Republic are obtained from the publicly accessible website of the European Center for Disease Prevention and Control. For the possibility of comparing current wastewater monitoring results (approx. for the last 1–2 months), freely available data from covid maps or publicly accessible websites for individual cities on the platform (in Czech) are used. Public data may contain errors and do not contain the number of inhabitants in the connected municipalities.

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

  • different amount of wastewater = different dilution of the amount of viral RNA fragments present,
  • by taking in another weekly regime (weekend),
  • inhomogeneity of the collected sample (waste water contains a number of other substances and particles, sampling is performed after mechanical removal of coarse impurities),
  • 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 Kateřina Sovová and an article in MF Dnes (in Czech) public journal from Hana Zvěřinová Mlejnková also deal with the topic.

Learn more about the ongoing project here.