There has been an attempt by some researchers to determine when the first cases of covid were detected in wastewater samples. There are three known studies so f

There has been an attempt by some researchers to determine when the first cases of covid were detected in wastewater samples. There are three known studies so far. December 2019 in Italy: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7428442/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7428442/ November 2019 in Brazil: https://www.medrxiv.org/content/10.1101/2020.06.26.20140731v1 https://www.medrxiv.org/content/10.1101/2020.06.26.20140731v... March 2019 in Spain: https://www.medrxiv.org/content/10.1101/2020.06.13.20129627v1 https://www.medrxiv.org/content/10.1101/2020.06.13.20129627v...