The wastewater concentration of coronavirus in Gothenburg, Sweden, has decreased sharply to a four-month lowest level, the University's latest measurements and analyses show.
The fourth wave of the COVID-19 pandemic has been the most prolonged of all. In 16 weekly measurements in a row, levels of SARS-CoV-2 in the wastewater of Gothenburg remained as high as, or higher than, the previous three waves' peak figures.
Starting with the water samples taken in mid-December 2021, the upturn culminated in a record high in samples from the week of January 10-16 2022. Since then, concentrations have fallen slightly but still gone on fluctuating at high levels.
However, the latest measurement - based on samples taken in the week of April 11-17 - reveals a sharp fall. Obviously, nothing is guaranteed for the weeks ahead, but the relief felt by Heléne Norder, microbiologist and head of the research group, is obvious.
Long-awaited result
"At last it's beginning to subside. We're now seeing the lowest number of SARS-CoV-2 in a long time," she says.
"It may be because the weather's starting to get warmer and the virus is following its seasonal pattern, as in 2021, when levels were low from late April to December. Let's hope no new variants will emerge that can cause severe illness and that, in the future, coronavirus just spreads like a common cold virus."
These investigations of SARS-CoV-2 levels in the Gothenburg wastewater have been underway since February 2020. They are performed by a research group at Sahlgrenska Academy, University of Gothenburg, assisted by Gryaab, the municipally owned company that treats wastewater in Gothenburg and surrounding municipalities.
Every week, Gryaab supplies the scientists with a sample composed of daily wastewater samples. After measuring and analyzing the weekly samples, the group reports directly to the Infection Control Unit and care providers in Västra Götaland.
Levels for other viruses
The amount of coronavirus in wastewater indicates the prevalence of the virus and associated disease (COVID-19) in the community. The connection between the virus level in the wastewater and the proportion of people who are severely ill has, however, weakened successively with the strengthening of protection afforded by vaccinations.
Besides SARS-CoV-2, the concentration of norovirus GG2 (the "winter vomiting bug") is also measured. According to the latest results, its level has now fallen for the fourth consecutive week, and this trend is in line with normal seasonal variation.
The concentration of enterovirus is fluctuating at a continued relatively high level. Enterovirus can cause a broad range of symptoms from the common cold to inflammation of the pericardium ((the fluid-filled, two-layered sac surrounding the heart), meningitis and paralysis, although most people infected get only mild symptoms.
