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Toilet visits contribute to surveillance of coronavirus infection

Wednesday 29 Apr 20

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Frank Møller Aarestrup
Professor, Head of Division
National Food Institute
+45 35 88 62 81

Analyzing sewage can reveal whether the number of COVID-19 infections in an area is increasing or decreasing, according to analyses from the Technical University of Denmark. Such analyses can also show whether changes in behaviour during the corona pandemic e.g. affects how many people get a foodborne illness or the occurrence of antimicrobial resistant bacteria.

Along with an international team of colleagues, researchers from the National Food Institute, Technical University of Denmark, have proven that analyzing sewage is a valuable disease surveillance tool, because sewage can reveal how many disease-causing microorganisms are present in people in a given collection area.

As part of its work to further develop a global surveillance system via sewage, every week for the past five years the institute has analysed six litres of sewage collected in the greater Copenhagen area to study changes in the analytical results. In recent weeks, the institute’s researchers have analyzed samples from the treatment plant Lynetten on Amager to look for the novel coronavirus SARS-CoV-2, which is found in the stool of infected people.

SARS-CoV-2 causes the illness COVID-19.



Come along to the treatment plan Lynetten where Jim Bogut takes a sample for the global sewage surveillance project, of which the National Food Institute is one of the initiators.

Sewage can reveal changes in the infection rate

There are several advantages to using sewage when analyzing for infection: No ethical approval is necessary, as the material cannot be traced back to individuals. Furthermore, the samples include material from people who feel well but do in fact have COVID-19. As such, data gives a good overview of the total number of infected persons in the collection area.

Although the analyses do not show the exact number of infected persons, data can show whether the COVID-19 infection rate—that is, how many people are sick with the infection—is increasing or decreasing. As such, sewage surveillance can give an early warning that a new wave of infections is coming.

Research colleagues from the global sewage project from e.g. the Netherlands, Spain, USA and New Zealand are also regularly analyzing sewage as a supplement to their national disease surveillance in order to gather as much information as possible in the fight against COVID-19. 

Sewage contains other valuable information

The National Food Institute has also set out to study whether Danes’ altered daily routines during the shutdown of Denmark can be detected in the presence of foodborne microorganisms in the collected sewage samples. That is, whether changes such as better hand hygiene, changed dietary habits and fewer visits to canteens and restaurants have an impact on the number of people that become ill from e.g., salmonella, campylobacter and norovirus.

Furthermore, the researchers are looking at the occurrence of antimicrobial resistant bacteria in the samples. Transmission of resistance often occurs through human contact. Therefore, it is likely that increased physical distance and a focus on e.g. sneezing into your elbow will have an effect on the occurrence of resistance. The researchers will determine this by comparing their analytical results with data on antimicrobial use.

Given that all non-critical research activities at the Technical University of Denmark are closed until further notice, these parts of the study will be completed at a later date.

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The National Food Institute’s is carrying out the work to create a global surveillance system for antimicrobial resistance with funds from the Novo Nordisk Foundation in a six-year long project. Through its involvement with the project, the institute also helps to support the UN's Sustainable Development Goal of ensuring healthy lives and promoting well-being for all. Read more on the project’s website: Global Surveillance.

About global sewage surveillance

The sewage sampling in Copenhagen in just a small part of a group of researchers’ big ambition of creating a global surveillance system via sewage. As part of their efforts to prove that analyzing sewage is a useful method for monitoring infectious diseases and antimicrobial resistant bacteria, the researchers have conducted four global prevalence studies in more than 250 cities in 103 countries around the world. Prevalence studies show a population’s state of health.

Read about the project in a news items from the National Food Institute: Sewage reveals levels of antimicrobial resistance worldwide