At 12 locations in Sweden, the Royal Institute of Technology (KTH) and the Swedish University of Agricultural Sciences (SLU) measure the amount of covid-19 virus in the wastewater to investigate the spread of infection in society.

In the last five weeks, an increase has been noted, albeit from low levels.  

Last week, a dramatic increase was noticed both in Stockholm and in Malmö.

This week's analyzed data, however, show a completely different picture.

In several places there is no increase at all and in Stockholm the levels have decreased.

But in general, the curve is going up.  

- The trend is that the spread of infection is increasing, says Maja Malmberg who is a researcher in virology at SLU.

Photo: Virus levels in Järva in Stockholm in 2021. A marked increase is seen in week 49 and a decrease in week 50.

Signs of the coming wave

Last week's figures from Stockholm are at the same level as just before the previous pandemic wave.

Even then, an increase was seen followed by a decrease.  

- It could be a sign of a coming wave, says Zeynep Cetecioglu Gurol, senior lecturer at KTH and project manager for the measurements of Stockholm and Malmö's waters.

No omikron cases

That the numbers go up and down from week to week is common in the measurements, explains Maja Malmberg, who believes that it is difficult to analyze wastewater.

- The method is not so super specific or super sensitive.

There is room for sources of error, she says.

Wastewater analysis is better for investigating infection trends over time than for detecting individual cases.

Last week, the researchers tested water in search of the omicron variant, without finding a single case.

The dominant variant was still delta.