Isolation of Polioviruses from Sewage and their Characteristics: Experience over Two Decades in Sweden

Abstract

Indigenous polio ceased in Sweden in 1962 after 5 years' use of killed polio vaccine. In 1967, it was considered of interest to investigate whether poliovirus was present in the sewage. A method for selective isolation of poliovirus from sewage was developed. The method appeared to increase the yield. The studies were carried out at intervals up to 1990. In 1989–90, the virus isolates were characterized by the use of monoclonal antibodies differentiating between vaccine-like (Sabin-like) and non-vaccine-like strains. Polioviruses of both kinds were isolated throughout the period. Two periods were of special interest. The first was in 1977, when a single, paralytic, type-2 case occurred in Sweden in an unvaccinated sect. The second was in 1984–85 when a type-3 epidemic broke out in Finland, followed by vaccinations of the whole Finnish population with live oral polio vaccine. On both occasions the implicated viruses could be traced to a high degree in sewage in Sweden. The absence of poliovirus isolations from faecal specimens of patients and the isolation of live poliovirus vaccine virus, i.e. a vaccine not used in Sweden, indicate that the virus strains are imported