High concentrations of the coronavirus SARS-CoV-2 are again being detected in wastewater in Leuven, reaching the highest levels in a year, KU Leuven virologist Elke Wollants said on Saturday.
The rise is particularly striking because the virus had been barely or not at all detectable in Leuven’s wastewater for almost a year.
Since monitoring began in 2021, Wollants said, there had never been such a long period with hardly any measurable concentrations.
The last clear peak was recorded in November 2025. From August 2026, concentrations began to rise again, with the increase accelerating sharply in recent weeks.
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According to Wollants, many people have not had the virus for a long time, meaning any built-up protection may have weakened and antibodies may have waned.
The return to school could also help drive transmission.
She said this was therefore a good time to get vaccinated against Covid-19, particularly for older people, those with weakened immune systems and other at-risk groups.
Vaccination also offers protection against long Covid, she said.
Wollants referred to a large European study published in The Lancet, which found that vaccination at population level was associated with about a 30-50% lower risk of long Covid.
The researcher also rejected claims circulating on social media that the high concentrations of the virus in wastewater were caused by vaccinations.
The PCR tests used by the Leuven team target the N gene of the SARS-CoV-2 virus, she said.
That genetic material is not present in mRNA vaccines, which contain only mRNA for the spike protein and which is also broken down quickly after vaccination.
“Everything we measure in the wastewater comes from circulating infections, not from vaccinations,” Wollants said.
