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Diseases & Vaccines / Vaccine-Preventable Diseases in EPI-SA / Poliomyelitis / Clinical Disease
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CLINICAL DISEASE: POLIOMYELITIS
inapparent infection without symptoms; minor illness; non-paralytic polio; paralytic polio.
Polio is a highly infectious disease caused by infection with the poliovirus. There are three types of poliovirus, types 1, 2 and 3. It is transmitted by the faecal-oral route and is spread from person to person by contaminated food and water or by saliva. The virus enters the body via the mouth, multiplies in the oropharynx or the gut, and then enters the blood system before disseminating into other parts of the body. Incubation ranges from 2 to 35 days with most infections being sub clinical. Poliovirus exposure is classified according to 4 categories:
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The majority of polio infections, 70-72% of all cases fall into this category.
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Most frequent form (24% of infections) of illness, with a duration of a few days. It is characterised by various combinations of the following: fever, nausea, malaise, drowsiness, headache, vomiting, constipation and sore throat.
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A relatively rare outcome (<4%) of polio that begins as a mild illness characterised by fever, sore throat, vomiting and malaise. One to two days later signs of meningeal irritation become apparent, and these include stiffness of the neck and back, severe headache, vomiting, and pain in the limbs, back and neck. The disease lasts 2 to 10 days and recovery is complete. A few cases can progress to the severe paralytic form.
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Occurs in less than 1% of infections. This is characterised by a minor illness of several days, followed by rapid onset of flaccid paralysis within a few days. The limb muscles are more prone to be affected than other muscles, resulting in paralysis of the limbs. In rare cases death occurs if the lung muscles are affected.
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