Spectre of SARS-CoV-2 RNA in the ambient urban waters of Ahmedabad and Guwahati: A tale of two Indian cities

Abstract

COVID-19 positive patients can egest live SARS-CoV-2 virus and viral genome fragments through faecal matter and urine, raising concerns about viral transmission through the faecal-oral route and/or contaminated aerosolized water. These concerns are amplified in many low- and middle-income countries, where raw sewage is often discharged into surface waterways and open defecation is common. Nonetheless, there has been no evidence of COVID-19 transmission via ambient urban water, and the virus viability in such aquatic matrices is believed to be minimal and not a matter of concern. In this manuscript, we attempt to discern the presence of SARS-CoV-2 genetic material (ORF-1ab, N and S genes) in the urban water (lakes, rivers, and drains) of the two Indian cities viz., Ahmedabad (AMD), in western India with 9 wastewater treatment plants (WWTPs) and Guwahati (GHY), in the north-east of the country with no such treatment facilities. The present study was carried out to establish the applicability of environmental water surveillance (E-wat-Surveillance) of COVID-19 as a potential tool for public health monitoring at the community level. 25.8% and 20% of the urban water samples had detectable SARS-CoV-2 RNA load in AMD and GHY, respectively. N-gene > S-gene > ORF-1ab-gene were readily detected in the urban surface water of AMD, whereas no such observable trend was noticed in the case of GHY. The high concentrations of SARS-CoV-2 genes (e.g., ORF-1ab; 800 copies/L for Sabarmati River, AMD and S-gene; 565 copies/L for Bharalu urban river, GHY) found in urban waters suggest that WWTPs do not always completely remove the virus genetic material and that E-wat-Surveillance of COVID-19 in cities/rural areas with poor sanitation is possible.

Keywords: COVID-19; SARS-CoV-2 RNA; Sewage; Surveillance; Urban water; Wastewater.