| The polioviruses are small, RNA-containing viruses, classified in the genus Enterovirus within the family Picornaviridae. APP can be caused by three polioviruses (type 1, 2, or 3). [2] A person infected with one of the types is still at risk of infection from either of the two remaining types. Infection with the poliovirus occurs by the fecal/oral route. The virus replicates in the gastrointestinal tract, where it can penetrate the mucosa and be carried by blood throughout the body. It is excreted primarily in the stool, but also to a lesser degree in oropharyngeal secretions. After infection, and also after administration of the OPV, fecal secretion of the virus can continue for at least several weeks. Because of this, transmission to other persons can still occur easily in areas with poor sanitation and overcrowding.[2] In addition, inadequately vaccinated caretakers of children recently vaccinated with the OPV are at risk for becoming infected. |