Early detection of SARS-CoV-2 infection cases or outbreaks at nursing homes by targeted wastewater tracking

Davo, L.; Segui, R.; Botija, P.; Beltran, M. J.; Albert, E.; Torres, I.; Lopez-Fernandez, P. A.; Orti, R.; Maestre, J. F.; Sanchez, G.; Navarro, D.

Objectives: Near-source tracking of SARS-CoV-2 RNA in the sewage drains serving particular buildings may allow rapid identification of SARS-CoV-2 infection cases or local outbreaks. In this pilot study, we investigated whether this was the case for nursing homes (NH). Methods: The study involved five NH (from A to E) affiliated to the Clinico-Malvarrosa Health Department, Valencia (Spain). These were nursing or mixed nursing/care homes of different sizes, altogether providing care for 472 residents attended by a staff of 309. Near-source sewage samples were screened for presence of SARS-CoV-2 RNA by RT-qPCR at least 5 days per week during the study period. SARS-CoV-2 RNA testing in nasopharyngeal swabs from residents and staff was performed with the TaqPath COVID-19 Combo Kit (Thermo Fisher Scientific, Massachusetts, USA). Results: SARS-CoV-2 RNA was detected in wastewater samples from four of the five NH. SARS-CoV-2 infection cases were documented in three of these four NH. Of the two NH without SARS-CoV-2 infection cases, no SARS-CoV-2 RNA was detected in sewer samples from one facility, while it was repeatedly detected in samples from the other. Presence of SARS-CoV-2 RNA in sewage preceded identification of isolated cases among residents or staff or outbreak declaration in two NH, with lag times ranging from 5 to 19 days. Conclusion: Our study demonstrated that intermittent or persistent detection of SARS-CoV-2 RNA in NH sewers can provide an early warning of subsequent individual cases or outbreaks in these facilities.