University of Tartu Professor Tanel Tenson, who heads up the study, said of this week's data that: "We have noted a slight increase in the virus amount. The last few weeks have also seen a steady increase in the number of cities where the Omicron strain is present."

"So far, this strain has not become widespread yet. However, it is probably only a matter of time, so it would be a good idea to take precautions during New Year celebrations, and prefer outdoor and smaller gatherings to crowded indoor events," Professor Tenson continued, according to a university press release.

This compared with record infection rates in some other countries, he said. 

The samples of wastewater – sewage, to be more precise – are taken at all population centers with more than 10,000 inhabitants, and some smaller centers where needed.

The readings reflect the situation of wastewater passing through a treatment plant over the preceding 24 hours, giving a reliable overview of the infection level in that town or city, whereas spot checks conducted at smaller towns reflect the situation at the moment of sampling. Since these are more likely to be affected by other factors, data over several weeks is required, to indicate trends.

The study's results are used by the Health Board (Terviseamet) to monitor changes in the outbreak dynamics, discover hidden outbreaks and provide early information to estimate the spread of the virus, ahead of clinical cases being detected.

The study is EU-funded and carried out in cooperation with the the Estonian Environmental Research Centre, along with the water companies operating the waste water treatment plants across Estonia.

In the new year, responsibility for the study is being taken over by the Health Board, though Tartu University researchers will still be retained as advisers, Tenson said.

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