SARS-CoV-2 RNA monitoring in wastewater as a potential early warning system for COVID-19 transmission in the community: A temporal case study

Abstract

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus which causes coronavirus disease (COVID-19), has spread rapidly across the globe infecting millions of people and causing significant health and economic impacts. Authorities are exploring complimentary approaches to monitor this infectious disease at the community level. Wastewater-based epidemiology (WBE) approaches to detect SARS-CoV-2 RNA in municipal wastewater are being implemented worldwide as an environmental surveillance approach to inform health authority decision-making. Owing to the extended excretion of SARS-CoV-2 RNA in stool, WBE can surveil large populated areas with a longer detection window providing unique information on the presence of pre-symptomatic and asymptomatic cases that are unlikely to be screened by clinical testing. Herein, we analysed SARS-CoV-2 RNA in 24-h composite wastewater samples (n = 63) from three wastewater treatment plants (WWTPs) in Brisbane, Queensland, Australia from 24th of February to 1st of May 2020. A total of 21 samples were positive for SARS-CoV-2, ranging from 135 to 11,992 gene copies (GC)/100 mL of wastewater. Detections were made in a Southern Brisbane WWTP in late February 2020, up to three weeks before the first clininal case was reported there. Wastewater samples were generally positive during the period with highest caseload data. The positive SARS-CoV-2 RNA detection in wastewater while there were limited clinical reported cases demonstrates the potential of WBE as an early warning system to identify hotspots and target localised public health responses, such as increased individual testing and the provision of health warnings.

Keywords: COVID-19; Pandemic; SARS-CoV-2; WBE; Wastewater based epidemiology.

Graphical abstract

Fig. 1

Sampling site locations and population density of studied catchments. A) Indicates the location within Australia where the Hospital and Health Service (HHS) areas were located, which was the main geographical location where COVID-19 cases were reported in Queensland. Queensland HHS are shown in white outline with the other state borders. B) The location of the WWTP catchments under study, layered against the Brisbane North and Brisbane South HHS in yellow and green, respectively. The main public hospitals accepting COVID-19 patients in the area are shown in red colour. Parts of WWTP B and WWTP C catchments are located in both Brisbane North and Brisbane South HHS, while WWTP A is located in Brisbane South HHS. C) Shows the population density of the 2 HHS. The main populous areas of the two HHS were within the 3 WWTP catchments under study (highlighted in white).

Fig. 2

Comparison between the detection of SARS-CoV-2 in wastewater samples, to the number of cases observed in areas covered by the wastewater treatment plants. A) Sample timeline of samples analysed for SARS-CoV-2, with positive samples shown in red. B) The percentage of sample detections that were positive for SARS-CoV-2 RNA (black line with grey fill) for the previous 7 days (left y axis) and the GC of RNA/100 mL (yellow, plotted to right y axis) for the previous 7 days. C) Cases of COVID-19 per day in the Brisbane North and Brisbane South Hospital and Health Service (HHS) districts (stacked barplot, left y axis), as well as the number of active cases (line graph, right y axis).