Long-term surveillance of SARS-CoV-2 RNA in wastewater in Baltimore

Abstract

Since it was declared a pandemic by the World Health Organization in March 2020, SARS-CoV-2 has been known to exhibit notoriety due to the number of people infected and dead over a period of three years. This study was to determine the presence of SARS-CoV-2 RNA viral fragments in wastewater samples from two wastewater treatment plants in Baltimore over a period of one year. The samples were concentrated by the Polyethylene Glycol 8000 (PEG) method, and RNA fragments were purified using the QiAmp Viral RNA Mini Kit. RT-PCR and qPCR assays were performed, and Cq values below 40 were analyzed and presented as gene copies/L. N1 and N2 genes were detected in both WWTP samples, with N1 having log10 gene copies ranging from 1.38 - 3.34 gc/l and N2 ranging from 1.88-3.20 gc/l. Covid19 hospitalization cases in Baltimore County and City were observed to be 40-42% positively correlated with the copies of N-genes detected in the WWTP-A. On the contrary, the N-genes (N1 and N2) from both WWTPs exhibited a very weak positive and negative relationship with wastewater physical parameters such as pH, electrical conductivity, total dissolved solutes, salinity, and temperature. The reduction in positive correlation with hospitalization cases could be attributed to an increase in immunity amongst the population in both counties surveyed. There is a need to ascertain the effect of physical parameters changes from the sampling point to the processing point on the capture and detection of SARS-CoV-2 viral RNA in wastewater.