Coronavirus level in wastewater is decreasing very slowly

This week’s results of the wastewater analysis led by the University of Tartu confirm a persistent yet very slow decline in the coronavirus levels. There is still a large amount of virus in wastewater samples all over Estonia and achieving a moderate level can still take weeks.

Based on the wastewater index describing the average situation in Estonia, the current spread of the virus is comparable to that of the beginning of February when the more rapid spread began. According to the lead researcher, Professor of Technology of Antimicrobial Compounds of the University of Tartu Tanel Tenson, the decline in the amount of virus in wastewater started in the second half of March and is now noticeable in all Estonian regions. “However, the decrease rate is very modest and the amount of virus in wastewater continues to be uniformly high across Estonia. Thus, it is still weeks before we can expect a significant change and reach the moderate level,” Tenson explained.

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, tanel.tenson@ut.ee