Non-intrusive wastewater surveillance for monitoring of a residential building for COVID-19 cases

Abstract

Wastewater-based surveillance for SARS-CoV-2 has been used for the early warning of transmission or objective trending of the population-level disease prevalence. Here, we describe a new use-case of conducting targeted wastewater surveillance to complement clinical testing for case identification in a small community at risk of COVID-19 transmission. On 2 July 2020, a cluster of COVID-19 cases in two unrelated households residing on different floors in the same stack of an apartment building was reported in Singapore. After cases were conveyed to healthcare facilities and six healthy household contacts were quarantined in their respective apartments, wastewater surveillance was implemented for the entire residential block. SARS-CoV-2 was subsequently detected in wastewaters in an increasing frequency and concentration, despite the absence of confirmed COVID-19 cases, suggesting the presence of fresh case/s in the building. Phone interviews of six residents in quarantine revealed that no one was symptomatic (fever/ respiratory illness). However, when nasopharyngeal swabs from six quarantined residents were tested by PCR tests, one was positive for SARS-CoV-2. The positive case reported episodes of diarrhea and the case's stool sample was also positive for SARS-CoV-2, explaining the SARS-CoV-2 spikes observed in wastewaters. After the case was conveyed to a healthcare facility, wastewaters continued to yield positive signals for five days, though with a decreasing intensity. This was attributed to the return of recovered cases, who had continued to shed the virus. Our findings demonstrate the utility of wastewater surveillance as a non-intrusive tool to monitor high-risk COVID-19 premises, which is able to trigger individual tests for case detection, highlighting a new use-case for wastewater testing.

SARS-CoV-2 shedding sources in wastewater and implications for wastewater-based epidemiology

“…In contrast to clinical testing, which determines the prevalence by testing individuals, wastewater-based epidemiology (WBE) is a promising approach for population-wide surveillance ( Hart and Halden, 2020a , Li et al, 2021a ). By systematic collections of wastewater samples either at the inlet of wastewater treatment plants (WWTPs), in sewer pumping stations, or manholes, the WBE approach provides a prevalence estimation with a single wastewater sample for the connected catchment or buildings ( Betancourt et al, 2021 , Rusiñol et al, 2021 , Wong et al, 2021 ). This requires much lower cost and effort compared with clinical testing for a community with a large population.…”

SARS-CoV-2 in wastewater: From detection to evaluation

“…In contrast to large community testing, WBE can also be used to test a small community for the presence of the virus. In Singapore, WBE was used as a form of non-intrusive surveillance method to monitor SARS-CoV-2 in residential blocks [ 58 ]. Despite the absence of confirmed COVID-19 cases, increased frequency and concentration of SARS-CoV-2 was detected in the wastewaters.…”

“…This is a successful cost-effective strategy to mitigate COVID-19 outbreaks, considering the substantial population of students living in on-campus dormitories. Through these studies, it is well-agreed that wastewater surveillance has the potential to act as a complementary strategy with clinical testing to maximize the probability of detecting COVID-19 cases in the community [ 48 , 57 , 58 , [61] , [62] , [63] ].…”

The devil is in the details: emerging insights on the relevance of wastewater surveillance for SARS-CoV-2 to public health

“…Chavarria-Miró et al (2021) were monitoring both wastewater influents to WWTPs and grab samples from urban sewers in Barcelona, Spain and when the WWTP samples declined to non-detectable levels, sewer monitoring identified COVID-19 hot spots that facilitated the adoption of local mitigation measures. Wong et al (2021) and Xu et al (2021) used sewer sampling in Singapore and Hong Kong, respectively, to identify hot spots in apartment buildings that guided clinical testing and quarantining requirements. Acosta et al (2021) sampled sewers that served acute care hospitals in Calgary, Canada, finding that the viral signals indicated the occurrence of hospital-acquired infections.…”