Wastewater study: Coronavirus level decreasing, but still high

The University of Tartu main building.
The University of Tartu main building. Source: Vladislava Snurnikova/ERR

There has been a decrease in coronavirus levels in wastewater, the University of Tartu's latest wastewater monitoring study shows. In several areas, it is at a low level.

At the same time, researchers acknowledge that the amount of virus in the wastewater is still considerable. The situation is particularly worrying in some of the larger towns in Ida-Viru County, where the amount of virus in wastewater continues to be above the Estonian average.

The current level of coronavirus in wastewater is comparable to that of early February.

The study's lead researcher Professor of Technology of Antimicrobial Compounds of the University of Tartu Tanel Tenson said this means that the overall concentration of the virus has started to stabilize, but is still quite high.

"The daily number of new infections continues to be around 300, which is still a lot higher than last October, for instance. This is also reflected in the wastewater samples we analyze," Tenson explained.

"However, we can be glad that the situation in some larger places such as Võru, Jõgeva and Loksa has considerably improved, in addition to several smaller places. It has been a while since we last saw that," he said.

Ida-Viru County is in a more critical situation in terms of the spread of coronavirus, and there the index describing the average situation is above the Estonian average.

"While the figure is below 100 in central and western Estonia, and around 200 in southern Estonia, it is as high as 300 in Ida-Viru County," Tenson said.

The indicator describing the average situation in Harju County is 250. According to Tenson, the situation has somewhat stabilized in that region, though there has been no significant decline. "We can only hope that the alleviation of restrictions will not lead to a sudden increase in the virus levels again," he said.

Results of the survey on May 10–14. Source: University of Tartu

How and where are the samples collected?

Wastewater samples are collected at the beginning of every week in all county centers, cities with more than 10,000 inhabitants and, if necessary, in smaller settlements.

Samples taken from larger cities reflect the situation of wastewater passing through the treatment plant over 24 hours, giving a reliable overview of the infection level in the city. In smaller places, spot samples are taken, showing the situation at the moment of sampling.

Spot samples are more easily affected by various factors and should therefore be used in comparison over several weeks to estimate the trend, rather than to get a definitive picture of the current situation.

The study is a tool helping the Health Board monitor changes in the outbreak dynamics and discover hidden outbreaks.


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Editor: Helen Wright

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