Research - Record wastewater monitoring - what does the evidence say about the coronavirus situation?
Just before Christmas, everyone is coughing and sniffling. The waiting rooms in many doctors' surgeries are full. According to the latest weekly report from the Robert Koch Institute (RKI), 7.9 million people in Germany are currently suffering from a respiratory infection. But how many coronavirus infections are among them?
During the pandemic years, people were diligently tested at home, in doctors' surgeries or test centers to find out whether a sore throat, runny nose and fever were due to a cold or whether they were infected with the coronavirus. The positive rapid test still had to be confirmed with a PCR test and the GP practice reported the case. This gave the RKI a good overview of the number of people infected with coronavirus.
A look at the corona pandemic radar reveals that the current 7-day incidence of reported cases is 38 (as of 15.12.23). As a reminder, the 7-day incidence provides information on how many people per 100,000 inhabitants have fallen ill with Covid-19 in the last seven days. At the height of the coronavirus pandemic in spring 2022, the 7-day incidence was almost 2,000. The bare figures make it sound as if almost nobody in Germany is currently infected with Covid-19. But it's not quite that simple.
Corona tests are no longer being carried out across the board
The situation is different today. We can take a coronavirus test voluntarily at home. Systematic testing is now only carried out in hospitals on symptomatic patients. This means that the 7-day incidence in 2022 cannot be compared with that of today. In order to better assess the situation of Covid-19 infections, the RKI is now using other methods. On the one hand, the RKI uses information from flu web participants to assess the coronavirus situation. According to the current weekly report, the estimated 7-day incidence is 2500 coronavirus infections per 100,000 inhabitants. The RKI also uses the findings of the SentiSurv study conducted by the Mainz University Medical Center for its estimates. For this, 10,000 representatively selected adults from Rhineland-Palatinate are tested once a week. SentiSurv arrives at a 7-day incidence of 3896 in Rhineland-Palatinate in the week up to December 13.
Secondly, the viral load in wastewater is measured. The viral load, with an average of almost one million gene copies in one liter of water, has reached its highest level since measurements began in June 2022. The latest data in the coronavirus pandemic radar goes up to November 29 (as at 12.12.23) . Wastewater monitoring is an important tool for identifying trends in the coronavirus situation. As described, scientists can no longer rely on the 7-day incidence as they did when testing was mandatory. The wastewater monitoring data shows that the viral load in wastewater has been increasing since the end of June 2023. A trend is therefore discernible.
Wastewater monitoring: trends are recognizable
But where does the wastewater monitoring data actually come from? The RKI currently receives data from 82 wastewater treatment plants in Germany. However, these are not selected to be representative. If a person is infected with Sars-CoV-2, he or she excretes the pathogen via stool, urine or saliva. By taking samples from wastewater from sewage treatment plants, scientists can therefore evaluate how high the viral load per liter of water is. To do this, the sample is processed in the laboratory and the coronavirus is detected using a PCR test. Monitoring the coronavirus in water is a supplementary measure to better assess the coronavirus situation. Wastewater monitoring provides information on the viral load and infection dynamics.
However, it is not possible to tell exactly how many people have contracted Covid-19. Infected people sometimes excrete more and sometimes less virus - depending on which variant they have been infected with or how long they have had the infection. It is also not possible to determine the severity of the infection or the burden on the healthcare system. This means that the data from wastewater monitoring is merely a supplement. In addition to Sars-CoV-2, other diseases could also be better monitored in the future.
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Source: www.stern.de
