Monitoreo de SARS-CoV-2 en aguas residuales a escala de zonas sanitarias- Ciudad de Córdoba, la tercera ola COVID-19

Abstract

Wastewater is a matrix that summarizes the population excretion of SARS-CoV-2, therefore, wastewater-based epidemiological surveillance is a complementary tool to clinical epidemiological surveillance. Objective: To monitor the circulation dynamics of SARS-CoV-2 in different sanitary zones of Córdoba city during the third wave of the COVID-19 epidemic in order to locate viral circulation critical points, to detect variants of concern (VOCs) and to increase the knowledge of the importance of viral localized monitoring.

63 sewage wastewater samples from seven sanitary zones (ZS) of the city of Córdoba and, 9 samples from the Bajo Grande WWTP (BG) were collected weekly, during december 2021-january 2022. Virus concentration: elution and precipitation with polyethylene glycol 6000. RNA extraction: MagNAPure 96- Roche. Genomic detection: DisCoVery SARS-CoV-2RT-PCR Detection Kit gene N and LightMix® Modular SARS and Wuhan CoV E-gene kit. Real-time RT-PCR VOC variants detection: TaqMan™ SARS-CoV-2 Mutation Panel (Applied Biosystems).

An increase in viral detection was recorded as the notification of COVID-19 cases increased in each SZ, identifying a differential circulation dynamics of VOCs, over time, in each SZ (DELTA circulation first, followed by the introduction of Omicron, the co-circulation of both and finally, only Omicron). Bajo Grande viral detection results summarized those obtained in the sanitary zones, having detected the SARS-COV-2 genome in the 100% of the samples and reflecting, first the population circulation of the DELTA variants, then the introduction of Omicron, followed by the co-circulation of both variants, to reflect finally, as of mid-January, only the circulation of the Omicron variant.

Monitoring Córdoba´s SZ identified neighborhoods with the highest viral circulation and the VOCs that circulated in that neighborhood geography. It provided a tool to strengthen the localized containment and the mitigation actions to limit viral expansion to other areas of the city and to reinforce viral testing actions. Wastewater monitoring in Bajo Grande reflected the circulation of SARS-CoV2 and viral variants in the population of the City of Córdoba and was predictive of the third wave of the COVID-19 epidemic.