Wastewater concentrations of the coronavirus SARS‑CoV‑2 in the Gothenburg area have risen, although from relatively low levels. This is clear from the past few weeks' measurements and analysis performed at the University of Gothenburg.
"The trend is clear: a gradual rise is underway, although the quantities aren't large," says Heléne Norder, adjunct professor of microbiology at the Department of Infectious Diseases, Sahlgrenska Academy, University of Gothenburg, and microbiologist at Sahlgrenska University Hospital.
Norder leads the group of virologists at the University's Institute of Biomedicine who have been investigating the concentrations of SARS‑CoV‑2 in wastewater since February 2020. The work is done in collaboration with the municipally owned company Gryaab, which treats wastewater from Gothenburg and surrounding municipalities. The sample that Gryaab sends the scientists weekly is composed of samples that have been collected daily.
Five times the lowest level
Following the decline in viral concentrations that began in the week of May 17-23, with the lowest readings in the first half of July, there has been a gradual rise. Although the concentrations remain relatively low - a tenth of the peak during the second wave of the pandemic - Norder says the latest results are a cause for concern.
"It's worrying because we're now up at five times the minimum level, and that's before the schools have opened properly. That means we have a spread, though not a large one, around Gothenburg. We aren't seeing clusters of the kind we've had before, but the spread is probably evenly distributed," she says.
Impact on health care unclear
During the pandemic, the research group has regularly reported to care providers and infection controllers in the West Götaland region. The rising SARS‑CoV‑2 concentration in wastewater is associated with the increasing spread of infection, and consequently a heavier burden on health care.
"What we can say is that the viral concentrations we're finding in the wastewater are related to the incidence of the disease, but we don't see an association with how seriously ill people become. Before we had a vaccine, we saw effects in health care after a week or so, and now we'll see how things go. It depends how many people have been vaccinated, since hospital care probably won't be necessary for those who have, if they become infected," Norder says.
"I hope the situation won't recur, but COVID-19 is an insidious disease in which the need for care doesn't usually arise until more than a week after onset. The importance of vaccination to avoid severe disease can't be emphasized enough."
