Coronavirus has been detected in the wastewater of several cities across Finland during August, according to the Finnish Institute for Health and Welfare (THL).
The virus was especially evident in wastewater samples taken from the Viikinmäki treatment plant in Helsinki, the Suomenoja plant in Espoo and the Kakolanmäki plant in Turku. Samples from the cities of Tampere, Rauma and Vaasa were also found to contain traces of the virus.
THL monitors the presence of coronavirus in wastewater by measuring the quantity of RNA, the virus's genetic mass, in samples collected from treatment plants, as RNA can be used to study the prevalence of coronavirus in the population.
The results can also help authorities predict and prepare for a spike in infections up to one week in advance.
Samples used to predict second wave
THL had introduced the monitoring of wastewater in the hope it could be used to predict whether the pandemic was speeding up or slowing down, and more recently to ascertain whether a second wave of the virus is becoming more likely.
However, it is not yet possible to deduce from the latest samples if an increase in the number of cases is likely.
"There is no exact information yet, as it is influenced by many factors. For example, how close to the treatment plant the infected person lives and what was the virus situation in relation to when the sample was taken," THL’s specialist researcher Tarja Pitkänen told Yle. "In the autumn, the goal is to get the number reliably reported so that the situation can be monitored at a local level."
Pitkänen added that although coronavirus has now been detected in wastewater in several locations, the virus will not end up being transmitted back into the environment from a treatment plant.
"Some samples of outgoing wastewater have been examined, and it appears that coronavirus remains in the wastewater treatment plant and does not end up in the environment," Pitkänen said.
Wastewater samples are collected weekly from five locations across Finland and monthly from 28 different treatment plants.