Confirmed Viruses Versus Unconfirmed Plaques in Sewage

Abstract

Ninety‐two treated and untreated sewage samples from seven wastewater treatment plants In Chicago, Illinois, Memphis, Tennessee, and Cincinnati, Ohio were examined for their virus content. Concentrated and unconcentrated samples were plaque assayed in five different cell culture systems. The virus etiology of plaques was confirmed by passage in homologous cell fluid cultures. Including all plaques tested, only 16.5 percent were confirmed as of viral origin. BGM cultures produced the greatest number of unconhrmable plaques. Confirmed virus concentrations for individual samples ranged from less than 0.2 to 80 PFU/1. Confirmed PFU's/1 averaged 0.7 for raw sewage, 0.5 for preliminary effluents and were not detected in final effluents. A strong recommendation of this study is that the virus etiology of all environmentally derived plaques must be confirmed.