Detection, Quantification, and Simplified Wastewater Surveillance Model of SARS-CoV-2 RNA in the Tijuana River

Abstract

The COVID-19 pandemic and the detection of SARS-CoV-2 RNA in sewage has expanded global interest in wastewater surveillance. However, many underserved communities throughout the world lack improved sanitation and use informal combined sanitary and storm sewer systems. Sewage is transported via open channels, ditches, and rivers, where it mixes with surface water and/or stormwater. There is a need to develop better methods for the surveillance of pathogens such as SARS-CoV-2 RNA in this context. We developed a simplified surveillance system and monitored flow rates and concentrations of SARS-CoV-2 RNA in the Tijuana River at two locations downstream of the United States–Mexico border in California, United States. SARS-CoV-2 RNA was detected in the upstream location on six out of eight occasions, two of which were at concentrations as high as those reported in untreated wastewater from California sanitary sewer systems. The virus was not detected in any of the eight samples collected at the downstream (estuarine) sampling location, despite the consistent detection of PMMoV RNA. Synchrony was observed between the number of cases reported in Tijuana and the SARS-CoV-2 RNA concentrations measured with the CDC N1 assay when the latter were normalized by the reported flow rates in the river.

Bacterial and Chemical Evidence of Coastal Water Pollution from the Tijuana River in Sea Spray Aerosol

“…CWP is transported by ocean currents and is a challenge to sample . We overcame this by directly sampling the TJR (TJRw in Figure ; SR 2-5), which was actively flowing into IB coastal waters throughout the study (Figure S1) and is a major pathway of CWP in the area. ,, …”

“…CWP at the Mexico–USA border between Tijuana (TJ), Mexico, and Imperial Beach (IB), USA, has persisted for decades and has been officially declared a state of emergency. ,, Whereas fecal and chemical pollution from stormwater runoff has been detected at various beaches in San Diego (SD), there is persistent and severe CWP at IB and TJ. ,,, Rains and inadequate infrastructure result in untreated sewage flowing into TJ–IB coastal waters. Hepatitis A virus and bacteria from TJ sewage have been detected in IB coastal waters. , The Tijuana River (TJR) is a major pollution conduit that sends 100-million-gallon sewage spills into South IB coastal waters. ,, SARS-CoV-2 has been detected in TJR waters at concentrations matching those at wastewater treatment plants . These problems caused IB beaches to be closed to water contact for 295 days 81 in 2020 .…”

“…coli) and Enterococcus spp. are bacteria used as sewage indicators, whereas enteroviruses, human norovirus, hepatitis A virus, and SARS-CoV2 are actual pathogens found in sewage-contaminated waters. − , Pathogens in coastal waters pose an immediate health threat because illness can occur from a single exposure. , …”

Presence and persistence of SARS-CoV-2 in aquatic environments: A mini-review

“…This has led to the extensive use of wastewater surveillance for containing and mitigating outbreaks [ 9 , 10 ]. Wastewater-based epidemiology has been used to predict community outbreaks in urban centers, universities, hospitals, and airplanes [ 11 ]. While wastewater surveillance has been impactful, it is relevant to know the presence and persistence of infectious SARS-CoV-2 in water and wastewater for the assessment of public health risks, that is, for describing the exposure risks associated with waters and wastewater to the public.…”

Detection of the SARS-CoV-2 Delta Variant in the Transboundary Rivers of Yunnan, China

“…Compared with the numerous reports of the presence of SARS-CoV-2 in wastewater systems during the pandemic, the number of studies reporting its incidence in freshwater or surface water is relatively limited (Table S1). River waters were positive for SARS-CoV-2 RNA in Nepal (4–5 × 10 4 copies/L), the Minas Gerais state of southern Brazil (1.1 × 10 5 copies/L), the Monterrey metropolitan area of Mexico (2.5–7.0 × 10 3 copies/L), the Danube River in Serbia (5.97 × 10 3 –1.32 × 10 4 copies/L), the Indian cities of Ahmedabad and Guwahati (800 copies/L for the Sabarmati River and 565 copies/L for the Bharalu urban river), and the Tijuana River at two locations downstream of the United States–Mexico border in California (10 3.4 –10 7.2 copies/L). River samples collected in Yamanashi Prefecture, Japan, between April 22 and May 7, 2020, were negative .…”