COVID-19 incidence is in good agreement with SARS-CoV-2 RNA numbers in wastewater in Finnish national surveillance
According to a national study by the Finnish Institute for Health and Welfare (THL), COVID-19 incidence is in good agreement with SARS-CoV-2 RNA numbers in wastewater.
Over the 10-month nationwide surveillance period, the detection rate of SARS-CoV-2 RNA in wastewater was 79%, while only 24% of all samples exhibited gene copy numbers above the quantification limit. The 95% probability to detect SARS-CoV-2 RNA in wastewater samples was reached when the 14-day COVID-19 incidence was 36 cases per 100 000 persons within the sewer network area.
However, the quantification of SARS-CoV-2 RNA fragments required significantly more COVID-19 cases: the 95% quantification rate was possible only after when the 14-day incidence was 223 COVID-19 cases per 100 000 persons. When the reported COVID-19 case number from the preceding 14 days was zero, less than 1% of the wastewater samples were positive with SARS-COV-2 RNA.
The dataset includes SARS-CoV-2 RNA copy numbers generated from wastewater samples and compared over time against the new and confirmed COVID-19 cases in the corresponding sewer network areas, from August 2020 to May 2021, covering wastewater of ca. 3.3 million inhabitants (~ 60% of the Finnish population).
“The coverage of the Finnish wastewater-based SARS-CoV-2 surveillance is very good at the national level”, says Tarja Pitkänen, Chief Specialist at THL.
Wastewater-based surveillance is a cost-effective concept for monitoring COVID-19 pandemics at a population level.
The members of the COVID-19 task force, dedicated to develop environmental surveillance of communicable diseases and working at the Finnish Institute for Health and Welfare THL, have now published as a preprint their findings of the wastewater-based surveillance covering nearly 700 wastewater influent samples from 28 wastewater treatment plants in Finland.
Wastewater-based surveillance of SARS-CoV-2 has been adopted in Finland as an indicator for local and national COVID-19 incidence trends. Importantly, the determination of SARS-CoV-2 RNA fragments from wastewater is a powerful surveillance measure, independent of possible changes in the clinical testing strategies or in the willingness of individuals to be tested for COVID-19.
Reference
Further information
Further information on Coronavirus Wasterwater Monitoring in Finland
Commission Recommendation on Coronavirus Wastewater MonitoringLink to an external websiteOpens in a new tab
Monitoring the Hybrid Strategy (only in Finnish and Swedish)
Tarja Pitkänen
Chief specialist
THL
tel. +358 29 524 6315
firstname.lastname@thl.fi
