Detection and quantification of SARS-CoV-2 RNA in wastewater influent in relation to reported COVID-19 incidence in Finland

Wastewater-based surveillance is a cost-effective concept for monitoring COVID-19 pandemics at a population level. Here, SARS-CoV-2 RNA was monitored from a total of 693 wastewater (WW) influent samples from 28 wastewater treatment plants (WWTP, N = 21-42 samples per WWTP) in Finland from August 2020 to May 2021, covering WW of ca. 3.3 million inhabitants ([~] 60% of the Finnish population). The relative quantity of SARS-CoV-2 RNA fragments in the 24h-composite samples was determined by using the ultrafiltration method followed by nucleic acid extraction and RT-qPCR assay targeted with N2-assay. SARS-CoV-2 RNA signals at each WWTP were compared over time to the numbers of new and confirmed COVID-19 cases in the sewer network area. Over the 10-month surveillance period, the detection rate of SARS-CoV-2 RNA in WW was 79% (including 6% uncertain results), while only 24% of all samples exhibited gene copy (GC) numbers above the quantification limit. The range of the SARS-CoV-2 detection rate in WW varied from 33% (including 10% uncertain results) in Pietarsaari to 100% in Espoo. Only six out of 693 WW samples were positive with SARS-COV-2 RNA when the reported COVID-19 case number from the preceding 14 days was zero. Overall, the 14-day COVID-19 incidence was 7, 18 and 36 cases within the sewer network area when the probability to detect SARS-CoV-2 RNA in wastewater samples was 50%, 75% and 95%, respectively. The quantification of SARS-CoV-2 GC required significantly more COVID-19 cases: the quantification rate was 50%, 75% and 95% when the 14-day incidence was 110, 152 and 223 COVID-19 cases, respectively, per 100 000 persons. Multiple linear regression confirmed the relationship between the COVID-19 incidence and the SARS-CoV-2 GC quantified in WW at 15 out of 28 WWTPs (overall R2 = 0.36, p < 0.001). At four of the 13 WWTPs where a significant relationship was not found, the GC of SARS-CoV-2 RNA remained below the quantification limit during the whole study period. In the five other WWTPs, the sewer coverage was less than 80% of the total population in the area and thus the COVID-19 cases may have been inhabitants from the areas not covered. Based on the results obtained, WW-based surveillance of SARS-CoV-2 could be used as an indicator for local and national COVID-19 incidence trends. Importantly, the determination of SARS-CoV-2 RNA fragments from WW is a powerful and non-invasive public health surveillance measure, independent of possible changes in the clinical testing strategies or in the willingness of individuals to be tested for COVID-19.

COVID-19 behavioural insights study: Preliminary findings from Finland, April-May, 2020

The COVID-19 monitoring behavioural insights study was conducted from April-May 2020 in Finland. Respondents reported feeling confident protecting themselves against COVID-19 infection. Worries shifted from overloading the health system (mean value 5.5 [95% CI: 5.4-5.6]) to mental health concerns (mean value 5.3 [95% CI 5.2-5.4]). Maintaining physical distancing from families and friends decreased by 7% and 6%. Respondents mostly agreed that if a vaccine would become available, they would get it. The decrease in acceptance of recommended measures needs further analysis, but current results provide evidence to support the response. Key pointsO_LICurrently limited information available on the complex interaction between epidemiology, media attention, pandemic control measures, risk perception and compliance with public health measures. C_LIO_LIDespite the relatively high risk perception of a possible infection with COVID-19, we observed a steady decrease in adherence to public health measures. C_LIO_LIThroughout the study, information-seeking behaviour shifted. C_LIO_LIWe observed a decrease in acceptance among the participants in regards to avoiding physical contact. C_LI

Laboratory-based surveillance of COVID-19 in the Greater Helsinki area, Finland, February-June 2020

Laboratory registry data (80,791 specimens, 70,517 individuals) was used to characterise age- and sex-specific SARS-CoV-2 RT-PCR sampling frequency and positivity rate, and laboratory capacity building in Greater Helsinki, Finland during February-June 2020. While the number of positive cases was similar in males and females, the positivity rate was significantly higher in males. The highest incidence/100,000 was observed in those aged [≥]80 years. The proportion of young adults in positive cases increased in late May 2020.