Concentration of coronavirus in waste water decreases steadily

The newest results of the waste water monitoring study led by the University of Tartu show a stable yet very slow decrease in the coronavirus levels. There are fewer samples with very high levels of virus, but the virus has not completely disappeared from any region.

Compared to the index describing the average situation in Estonia, the virus level is considerably higher in Ida-Viru County, southern Estonia and Harju County. “While the curve of the graph describing the change in the situation has turned downward everywhere, this decline is the slowest in Ida-Viru County and southern Estonia,” explained Tanel Tenson, Professor of Technology of Antimicrobial Compounds of the University of Tartu. The index describing the average situation in Estonia is still comparable to that of early February.

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,