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

This study was to determine the presence of SARS-CoV-2 RNA 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 extracted using the QIAamp 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 ranging from 1.38 to 3.34 log10 gc/l and N2 ranging from 1.88 to 3.20 log10 gc/l. COVID-19 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 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 RNA in wastewater.