Omicron spotted in Finnish wastewater in several regions

The coronavirus variant Omicron was detected in Finnish wastewater at several places in the country during the recent period, said the Finnish Institute for Health and Welfare (THL) in a press release on Wednesday.

The first confirmed detection of the Omicron in Finnish wastewater was obtained from an untreated wastewater sample from the Suomenoja wastewater treatment plant in Espoo. The sample was collected in between 6 and 7 December 2021.

THL began developing a method for identifying coronavirus variants from wastewater samples at the end of last year.

The identification of coronavirus variants in wastewater is possible with advanced sequencing techniques, even though Coronavirus’s genetic material, viral RNA, is diluted in wastewater and may be damaged by environmental factors.

Another detection of the Omicron variant was confirmed from the sample collected from the Viikinmäki wastewater treatment plant in Helsinki on 12–13 December 2021.

There were further detections of the Omicron variant in the samples collected in the following week between 19 and 20 December 2021. The variant was found in the wastewater treatment plants in Helsinki’s Viikinmäki in the Helsinki and Uusimaa Hospital District, Tampere’s Viinikanlahti in Pirkanmaa, Joensuu’s Kuhasalo in North Karelia, Pori’s Luotsinmäki in Satakunta and Turku’s Kakolanmäki in Southwest Finland.

An Omicron variant detection in a wastewater sample collected from Kuopio’s Lehtoniemi treatment plant in North Savo remained uncertain. The Omicron variant has not been detected in the previous weeks or other monitored localities.

The preliminary Omicron variant wastewater findings occurred at the time when the Omicron variant’s proportion of diagnosed coronavirus infections began to increase among the population in the area before Christmas.

According to the Finnish National Infectious Diseases Register, a total of 20 Omicron variant infections confirmed by sequencing have been diagnosed in the test positive samples collected by 5 December 2021. Nine of the infections were in the Helsinki and Uusimaa Hospital District and 11 in other hospital districts.

In November, all coronavirus variants detected in wastewater represented the Delta variant. In the wastewater examined in December, at first only the Delta variant could be detected and, later, the Omicron variant alongside it.

On 2 December 2021, THL reported the first coronavirus infection caused by the Omicron variant after which infections caused by the variant have been confirmed to an increasing extent. At the moment, the Omicron variant is becoming or has already become the dominant virus in the majority of regions.

Currently, the variant identification method only produces preliminary results from wastewater, and a sequencing delay of up to one month slows down the completion of results.

Not all collected wastewater samples have yet been analysed for coronavirus variants. The next sequencing results will be obtained in February at the earliest. The results concern the situation in different localities at the beginning of January.

After the turn of the year, wastewater monitoring samples have been collected during three weeks already. Based on the latest wastewater samples collected between 16 and 17 January 2022, the total number of coronavirus RNA in wastewater continues to increase.

On the basis of the last five measurements, coronavirus RNA numbers have continued rising in most of the examined wastewater treatment plants.

In Espoo, Helsinki, Hämeenlinna, Joensuu, Kuopio and Vaasa, the number of viral RNA copies per 1,000 people per day is the highest ever recorded for the second week in a row.

The numbers of coronavirus observed by wastewater monitoring are independent from clinical testing activity, and wastewater monitoring supports other epidemic indicators.

The coronavirus RNA numbers are examined weekly from the wastewater samples of 13 localities.

The wastewater treatment plants in Espoo, Helsinki, Hämeenlinna, Joensuu, Jyväskylä, Kouvola, Kuopio, Lappeenranta, Oulu, Pori, Tampere, Turku and Vaasa. In addition, a sample is collected from Rovaniemi every two weeks.