These come from people who have been given the oral polio vaccine in another country and then travel to the UK.
People given the oral vaccine can shed the weakened live virus used in the vaccine in their faeces for several weeks.
In response to the detection of the virus, the NHS will contact parents of children who are not up to date with their polio vaccinations.
The UK switched from using the oral polio vaccine (OPV) to an inactivated polio vaccine (IPV), given by injection, in 2004.The shots are given in routine NHS childhood vaccinations at eight, 12 and 16 weeks as part of the 6-in-1 vaccine.