An outbreak of polio has occurred in the American state of Minnesota which has affected four children with no paralysis. The outbreak happened in the Amish community who typically do not vaccinate their children and are isolated from outsiders. The last outbreak of polio in the US was in the Amish community in 1979.
Analysis of the virus showed that it is a vaccine-derived Sabin oral poliovirus 1. The OPV has not been used in the US since 2000 and only IPV is used. Vaccine-derived polioviruses emerge from OPV as a result of their continuous replication in immunodeficient persons or their circulation in populations with low vaccination coverage.
This outbreak further raises questions about what to do once the world has been declared free of wild-poliovirus as the vaccine being used to achieve this is most often the OPV. For example in South Africa where OPV is used, vaccine-derived polioviruses are prevalent in sewage and river water (Pavlov et al, 2005).
