Waste water analysis map includes several green spots after a long time

This week’s results of the waste water monitoring study led by the University of Tartu show a decrease in coronavirus levels. The results of the analysis show that in several Estonian settlements, the concentration of virus in waste water is back to a low level. At the same time, researchers acknowledge that the amount of virus in the waste water is still considerable. The situation is particularly worrying in some of the larger towns in Ida-Viru County, where the amount of virus in waste water continues to be above the Estonian average.

The current level of coronavirus in waste water is comparable to that of early February. According to the lead researcher of the study, Professor of Technology of Antimicrobial Compounds of the University of Tartu Tanel Tenson, this means that the overall concentration of the virus has somewhat stabilised, 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 waste water samples we analyse,” 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 stabilised 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.

How and where are the samples collected?

Waste water samples are collected at the beginning of every week in all county centres, cities with more than 10,000 inhabitants and, if necessary, in smaller settlements. Samples taken from larger cities reflect the situation of waste water 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. It gives early information for estimating the spread of the virus before clinical cases are detected. The Health Board is regularly informed of the results.

In collecting the samples, the University of Tartu cooperates with the Estonian Environmental Research Centre and water companies operating the waste water treatment plants of Estonian cities. The samples are analysed at the laboratories of the University of Tartu Institute of Technology. For more information and the interactive map with the previous results of the study, see the home page of the study “Detecting coronavirus in waste water”.

Further information: Tanel Tenson, Professor of Technology of Antimicrobial Compounds of the University of Tartu, 5344 5202, tanel.tenson@ut.ee