Amount of coronavirus in waste water remains stable

This week’s results of the waste water analysis led by the University of Tartu indicate that the concentration of coronavirus in waste water has remained rather stable over the past few weeks. Compared to the modest decrease in the Estonian average indicators, Harju County stands out by a somewhat quicker decrease in coronavirus level in the waste water.

The leader of the study, UT Professor of Technology of Antimicrobial Compounds Tanel Tenson says that the index illustrating the average situation in Estonia shows that in general, the concentration of coronavirus in waste water has remained about the same throughout April. “We do, however, see a slow decrease,” said Tenson.

To better illustrate the subtle change for the better, a new colour marker has been added to the map to differentiate high virus levels from very high. The results reveal that no region can be considered free from the virus yet. Rather the indicators confirming very high virus levels have been gradually replaced by somewhat lower levels over the past month.

How and where are the samples collected?

Wastewater 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 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 virus level in wastewater at the moment of sampling. Spot samples are more easily affected by various factors and should therefore be used over several weeks to estimate the trend, rather than 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, University of Tartu, 5344 5202,