Persistence of SARS-CoV-2 and its surrogate, bacteriophage Phi6, on surfaces and in water.

The COVID-19 pandemic spurred research on the persistence of infectious SARS-CoV-2 and its surrogates, including bacteriophage Phi6, in environmental reservoirs. Despite the wide use of Phi6, side-by-side comparisons between Phi6 and SARS-CoV-2 are limited. Here, we quantified the persistence of SARS-CoV-2 and Phi6 on surfaces (PVC plastic and stainless steel), using an initial inoculum of 10 3 plaque forming unit per surface, and evaluated the influence of four commonly used deposition solutions on viral persistence. In addition, we quantified the persistence of SARS-CoV-2 and Phi6 in water. Our findings revealed that Phi6 had a significantly longer half-life than SARS-CoV-2 in water and on surfaces. Phi6 persisted 34 hours in water compared with 13 hours for SARS-CoV-2. Viral persistence on surfaces was significantly influenced by the virus used and the deposition solution but not by the surface material. Phi6 remained infectious significantly longer than SARS-CoV-2 when the inoculation solution was culture media and saliva, leading to half-lives between 9 hours and 2 weeks for Phi6, compared to 0.5-2 hours for SARS-CoV-2. Using phosphate-buffered saline as a deposition solution led to half-lives shorter than 4 hours for both viruses on all surfaces. Our results indicate that bacteriophage Phi6 may lead to an overestimate of infectiousness for studies quantifying SARS-CoV-2 persistence on surfaces and water and highlight the importance of using appropriate deposition solutions when evaluating viral persistence on surfaces.IMPORTANCEThe COVID-19 pandemic spurred research on the persistence of SARS-CoV-2 and its surrogates. Here we highlight the importance of evaluating viral surrogates and experimental methodologies when studying pathogen survival in the environment.