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 Monitoring
Monitoring the Hybrid Strategy (only in Finnish and Swedish)
Tarja Pitkänen
Chief specialist
THL
tel. +358 29 524 6315
[email protected]
