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Poliovirus Case

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Eradicating a Virus

Polio became a major health issue around the world in the early 20th century. A tiny virus in structure caused many complications. New York, USA was the first to have a large-scale endemic with over nine thousand cases and around six thousand deaths ("History of Polio," 2012). In 1952, there were a reported 57,628 cases, with over 21,000 cases being paralytic ("History of Polio," 2012). Polio endemics were being seen around the world, mostly effecting children and causing eye and lower limb paralysis. It became important to find a way to eliminate the virus, and many stood up to help the cause.

Poliovirus is one of the smallest and simplest viruses known to man. It is a non-enveloped, icosahedral shaped virus that contains a single-, positive-stranded messenger RNA (Adu, 2005). The RNA encodes a large polyprotein which is cleaved into three precursor proteins (Adu, 2005). Its linear genome is approximately 7440 nucleotides in length (Percival, 2004). The overall diameter of the poliovirus is 27-30 nanometers on average (Adu, 2005). It is a member of the picornovirus family with genus is enterovirus, so it is similar to other common human pathogens, such as rhinovirus or hepatitis A (Percival, 2004). It is highly contagious and comes in three forms: PV1, PV2, and PV3. PV1 is the version of poliovirus that can cause infantile paralysis (Percival, 2004).

Poliovirus enters through the mouth, either by ingestion of food or water that is fecally contaminated. It attaches to the cells of the oropharynx, where is it replicated, swallowed, and then can later attach to the cells of the intestines (Percival, 2004). Poliovirus manages to survive passage through the stomach due to its ability to remain stable under acidic conditions (Percival, 2004). Infection leads to circulating viruses in the bloodstream which could potentially reach the central nervous system, spread to nerve fibers, and destroy motor neurons (Polio: How the Poliovirus Works, 2012). Motor neurons are important because they are the controllers of the muscles responsible for swallowing, circulation, respiration, and the muscles of the sub-cranial body (Polio: How the Poliovirus Works, 2012). The virus exits the body via feces (Percival, 2004).

To diagnose, initially, doctors observe for physical symptoms. They check for abnormal reflexes, back stiffness, difficulty swallowing and lifting the head or legs, and stiff neck (Poliomyelitis, 2012). Levels of polio antibodies and the virus itself are checked (Poliomyelitis, 2012). When needed, it is with the feces and a sample of throat secretions, and at times cerebrospinal fluid, from the patient that doctors can detect for the presence of the poliovirus and make a diagnosis (Percival, 2004).

Even as of now, there are no drugs that can eliminate poliovirus or successfully cure all of its symptoms.



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