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. 2024 Oct 29;12(11):2174.
doi: 10.3390/microorganisms12112174.

Wastewater Surveillance of SARS-CoV-2 in Slovenia: Key Public Health Tool in Endemic Time of COVID-19

Natalija Kranjec  1 , Andrej Steyer  2 , Tjaša Cerar Kišek  2 , Tom Koritnik  2 , Tea Janko  2 , Maja Bolješić  2 , Vid Vedlin  2 , Verica Mioč  2 , Barbara Lasecky  2 , Tatjana Jurša  2 , José Gonçalves  3 , Herbert Oberacher  4 , Alenka Trop Skaza  1 , Mario Fafangel  1 , An Galičič  1
Affiliations

Wastewater Surveillance of SARS-CoV-2 in Slovenia: Key Public Health Tool in Endemic Time of COVID-19

Natalija Kranjec et al. Microorganisms. .

Abstract

With the reclassification of COVID-19 as an endemic disease and the relaxation of measures, Slovenia needed a complementary system for monitoring SARS-CoV-2 infections. This article provides an overview of the epidemiological situation of SARS-CoV-2 in Slovenia using a wastewater surveillance system, demonstrating its usefulness as a complementary tool in epidemiological surveillance. This study found that estimated SARS-CoV-2 infections in Slovenia peaked in September 2022 and showed a declining trend with subsequent lower peaks in March-April and December 2023, mirroring the trends observed from clinical data. Based on both surveillance systems, the most prevalent variant in 2022 was BA.5. By 2023, BQ.1 and other Omicron variants increased in prevalence. By the end of 2023, XBB sublineages and the BA.2.86 variant had become predominant, demonstrating consistent dynamic shifts in variant distribution across both monitoring methods. This study found that wastewater surveillance at wastewater treatment plants in Slovenia effectively tracked SARS-CoV-2 infection trends, showing a moderate to strong correlation with clinical data and providing early indications of changes in infection trends and variant emergence. Despite limitations during periods of low virus concentration, the system proved significant in providing early warnings of infection trends and variant emergence, thus enhancing public health response capabilities.

Keywords: COVID-19; SARS-CoV-2; sewage; wastewater-based epidemiology; wastewater-based surveillance.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Timeline of weekly number of clinically tested individuals and positive cases per 100,000 inhabitants, 5 September 2022–31 December 2023, Slovenia [4].
Figure 2
Figure 2
Percentage of samples from clinical cases that underwent sequence analysis [4].
Figure 3
Figure 3
Catchment areas of the wastewater surveillance in Slovenia (green color).
Figure 4
Figure 4
Time-series plot of the estimated number of SARS-CoV-2 infections per 100,000 inhabitants in Slovenia and the number of active clinically confirmed SARS-CoV-2 infections per 100,000 people in the catchment population.
Figure 5
Figure 5
Abundance of SARS-CoV-2 variants, as determined based on the wastewater data, Slovenia, September 2022–December 2023.
Figure 6
Figure 6
Timeline of SARS-CoV-2 variant abundances in clinical cases, Slovenia, September 2022–December 2023 [4].
Figure 7
Figure 7
Distribution of total wastewater burden percentage by WWTPs size [9].
See this image and copyright information in PMC

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