Wastewater-based epidemiology concept as an early warning system for SARS-CoV-2 trend and its circulating variants in a defined catchment

Results

Phase 2 – Untreated wastewater monitoring campaign. Demonstration of SARS-CoV-2 infectivity from untreated wastewater (January 1, 2023 to December 31, 2023)

The results obtained during the Bucharest wastewater monitoring campaign followed the trend of epidemiological data, both the incident per 14 days per 100,000 inhabitants and the number of reported daily cases. The total concentration of SARS-CoV-2 viral particles ranged between 1.23×105 – 8.70×107 genomic copies (cg) per L, with an average of 5.63×106 cg/L in the untreated grab wastewater samples from the Hospital for Infectious and Tropical Diseases Dr. Victor Babes, 1.81×103 – 2.99×106 cg/L, with an average of 6.23×105 cg/L for the untreated composite wastewater samples and 4.63×101 – 1.74×106 cg/L, with an average of 3.71×105 cg/L for untreated grab wastewater samples from Wastewater Treatment Plant Glina Bucharest. The results obtained after data normalization regarding the concentration of SARS-CoV-2 to the population equivalent indicate a concentration of approximately 2 orders of magnitude higher than the raw concentrations. The concept of wastewater-based epidemiology and the integration of all calculations will be discussed in the next phase report (June 2024).

Regarding the isolation of the virus in cell cultures, we used untreated wastewater samples collected from the Wastewater Treatment Plant (48 composite samples and 48 grab samples) and 47 untreated grab wastewater samples from the Hospital for Infectious and Tropical Diseases Dr. Victor Babes, but few viruses were isolated. The isolation of SARS-CoV-2 on cell cultures remains a difficult approach, on one hand due to the low concentration of the isolated virus and the competition with the other viruses present in the wastewater samples, and on the other hand due to the presence of inhibitory substances in the wastewater samples (concentrated together with the virus).

In conclusion, the results obtained in the second phase of the WARNING project, during the wastewater monitoring campaign are in line with the objectives from the grant agreement and reflect a good performance of the activities, both the optimized laboratory protocols and the expected results.