Survivability of Delta and Omicron variants of SARS-CoV-2 in wastewater

Concerns of fecal-aerosol transmission of coronavirus disease 2019 (COVID-2019) coupled with increased transmissibility and disease severity of Delta and Omicron variants of concern (VOC) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), suggest studies on survival of VOC in wastewater are warranted. To the best of our knowledge, this is the first study to investigate the survivability of Delta and Omicron VOC in filtered and unfiltered raw wastewater, and secondary effluent at room temperature (23 °C). The time required for 90 % inactivation (T₉₀) of Delta and Omicron VOC in unfiltered raw wastewater was calculated as 17.7 and 15.3 h, respectively. Rapid inactivation of VOC in wastewater and inability to isolate SARS-CoV-2 in wastewater suggest risks from fecal-aerosol transmission are low. Nevertheless, high transmissibility of VOC cautions overruling fecal-aerosol transmission of COVID-19. Future studies on survival of SARS-CoV-2 in wastewater should attempt viral culture by spiking feces collected from COVID-19 infected patients into wastewater to match the real-world scenario.