This is a very important and timely paper on the pathway to widespread monitoring of SARS-CoV-2 RNA is in sewage for the purpose of wastewater-based epidemiology.
It’s increasingly difficult to keep track of all of the papers that have been put forward, either as published journal papers or (non-peer reviewed) preprints, on this topic. Though some that we’ve been keeping an eye on include papers from The Netherlands, Brisbane (Australia), Paris (France), Massachusetts (USA), Connecticut (USA), Montana (USA), Milan and Rome (Italy) Milan (Italy), Spain and Japan.
One thing that is quickly observable by reading these papers is a lack of any methodological standardisation. Very little work has seriously attempted to compare alternative approaches to key methodological aspects such as extraction and concentration of RNA from sewage.
But that is exactly what this paper contributes. It is based on recovery experiments with a different virus, murine hepatitis virus (MHV). This virus is often considered to be an appropriate surrogate for SARS-CoV-2 since it is an enveloped and positive-sense single-stranded RNA virus, belonging to the same genus as SARS-CoV-2.
The authors of this study tested virus RNA recovery from wastewater by seven diverse methods:
- Adsorption-extraction with three different pre-treatment options,
- Centrifugal concentration with two different devices,
- Polyethylene glycol concentration, and
The mean RNA recoveries ranged from 27-66%. The two most efficient methods were adsorption-extraction methods, with MgCl2 pre-treatment or without manipulation being the best performing. The third most efficient method used centrifugation, for which recovery efficiency was not statistically different from the two most efficient methods.
The authors concluded that adsorption-extraction methods with minimal pre-treatment or without manipulation can provide suitably rapid, cost-effective and relatively straightforward recovery of enveloped viruses in wastewater.
Ahmed W, Bertsch P, Bivins A, Bibby K, Farkas K, Gathercole A, Haramoto E, Gyawali P, Korajkic A, McMinn BR, Mueller J, Simpson S, Smith WJM, Symonds EM, Thomas KV, Verhagen R and Kitajima M (2020) Comparison of virus concentration methods for the RT-qPCR-based recovery of murine hepatitis virus, a surrogate for SARS-CoV-2 from untreated wastewater. Science of the Total Environment, 139960