Poliovirus surveillance by examining sewage specimens. Quantitative recovery of virus after introduction into sewerage at remote upstream location

In order to assess the feasibility of environmental poliovirus surveillance, known amounts of poliovirus type 1, strain Sabin, were flushed into the sewage network of Helsinki. Grab specimens collected at a remote downstream location and concentrated about a 100-fold revealed infectious poliovirus on four successive days in all three separate experiments. As for concentration, a simple two-phase separation method was found to be at least as useful as a several-fold more resource-demanding polyethylene glycol (PEG) precipitation method. Recovery of the introduced virus was remarkably high (more than 10%). Using the current system, it might be possible to detect poliovirus circulation in a population of 700,000 people by examining a single 400 ml sewage specimen, if 1 out of 10,000 inhabitants were excreting the virus. It is concluded that environmental surveillance is a sensitive approach to monitor silent poliovirus circulation in populations served by a sewage network.