Surveillance of SARS-CoV-2 spread using wastewater-based epidemiology: Comprehensive study

Abstract

SARS-CoV-2 pandemic is having a devastating effect on human lives. Recent reports have shown that majority of the individuals recovered from COVID-19 have serious health complications, which is going to be a huge economic burden globally. Given the wide-spread transmission of SARS-CoV-2 it is almost impossible to test every individual in densely populated countries. Recent reports have shown that sewage-based surveillance can be used as holistic approach to understand the spread of the pandemic within a population or area. Here we have estimated the spread of SARS-CoV-2 in the city of Hyderabad, India, which is a home for nearly 10 million people. The sewage samples were collected from all the major sewage treatment plants (STPs) and were processed for detecting the viral genome using the standard Reverse Transcription Polymerase Chain Reaction (RT-PCR) method. Interestingly, inlet samples of STPs were positive for SARS-CoV-2, while the outlets were negative, which indicates that the standard sewage treatment methods are efficient in eliminating the SARS-CoV-2 viral particles. Based on the detected viral gene copies per litre and viral particle shedding per individual, the total number of individuals exposed to SARS-CoV-2 was estimated. Through this study we suggest that sewage-based surveillance is an effective approach to study the infection dynamics, which helps in efficient management of the SARS-CoV-2 spread.

Keywords: COVID-19; Inactivation; Infectivity; RNA; RT-PCR; Sewage.

Graphical abstract

Fig. 1

The standard curves of a) E- gene, b) N-gene and c) ORF1ab gene, plotted with C_T values from log₁₀ dilutions of SARS-CoV-2 RNA. d) Plot representing the linear fit of all three genes C_T values.

Fig. 2

Concentration of sodium hypochlorite affects the detection ability of SARS-CoV-2 RNA. Scatter plot showing the effect of different concentrations of sodium hypochlorite on the C_T values of viral targets. Each dot represents average C_T values obtained from two replicates and the bar represents the standard error of mean.

Fig. 3

Degradation of Viral genome with time. Scatter plot showing the degradation of viral genome with the span of 24 days. Each dot represents average CT values obtained from two replicates and the bar represents the standard error of mean.

Fig. 4

SARS-CoV-2 RNA is present in Hyderabad's sewage water: Heat map showing the C_T values of E gene, N gene, and ORF1ab in the wastewater samples collected from various STPs in the city of Hyderabad on different days during the pandemic. The experiments were performed in duplicates or triplicates. Dark brown cells correspond to samples with no amplification. MLD-Million Litres per Day; ET-Equalization Tank; SC-Secondary Clarifier. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)