Poliovirus: Polio Immunization Plus

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Poliovirus is from the subgroup enterovirus and the family Picornaviradae. It is a virus that causes poliomyelitis, which is better known as polio. Poliovirus is usually contracted by the fecal-oral route, but sometimes infects by the oral-oral route. Once ingested, it is thought that poliovirus first infects the epithelial cells in the mucosa of the gastrointestinal tract and then spreads to the submucosal lymphoid tissue. This is when the first mild symptoms of poliomyelitis occur. These symptoms include fever, fatigue, vomiting, stiffness in the neck, and pain in the limbs. Paralysis occurs when poliovirus enters the central nervous system through the peripheral nerves or during viremia. The paralysis is usually in the legs, but poliovirus can cause total paralysis in a matter of hours. Poliovirus has a protein capsid which is 28 to 30nm thick and contains 12 capsomeres. It has a single strand of RNA. There are no spikes on poliovirus and it is nonenveloped. Poliovirus has a symmetrical icosahedral shape. Humans are the only known reservoir of polio. Polio can be vaccinated against, which usually happens during childhood.

The vaccine most commonly used to prevent poliomyelitis contains a weakened poliovirus. Rarely, the weakened virus in the vaccine mutates and causes a vaccine derived polio virus (VDPV). In the summer of 2003, an outbreak of VDPV plagued northern Nigeria. After the outbreak of the vaccine-induced virus, the vaccine was banned by Muslim clerics and politicians from the area. The ban was eventually lifted about a year later when tests showed that the vaccine was safe to use. Some clerics and parents still remained skeptical about the vaccine though. To make matters worse, since 2005, there have been 69 cases of VDPV which caused paralysis of Nigerian children. Many healthcare workers are concerned that this newest outbreak could cause more problems in the fight to eradicate polio globally. There was some good news however. Rates of...
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