An acute and sometimes devastating viral disease. Man is the only natural host for poliovirus. The virus enters the mouth and multiplies in lymphoid tissues in the pharynx and intestine. Small numbers of virus enter the blood and go to other sites where the virus multiplies more extensively. Another round of viremia (virus in the bloodstream) leads to invasion of the central nervous system (CNS), the spinal cord and brain, the key sites struck by the virus. In polio, there is inflammation of the central nervous system, especially the anterior horn cells of the spinal cord and the brainstem (the portion of the brain between the cerebral hemispheres and spinal cord). Polio can be a minor illness, as it is in 80-90% of clinical infections, chiefly in young children, and not involve the CNS. Symptoms are slight fever, malaise, headache, sore throat, and vomiting 3-5 days after exposure. Recovery occurs in 24-72 hours. This is termed the abortive type of polio. Polio as a major illness may or may not be paralytic. Symptoms usually appear without prior illness, particularly in older children and adults, 7-14 days after exposure. Symptoms are fever, severe headache, stiff neck and back, deep muscle pain, and sometimes areas of hyperesthesia (increased sensation) and paresthesia (altered sensation). There may be no further progression from this picture of viral meningitis or there be loss of tendon reflexes and weakness or paralysis of muscle groups. Recovery is complete in the abortive and nonparalytic forms of polio. In paralytic polio, about 50% of patients recover with no residual paralysis, about 25% are left with mild disabilities, and the remaining patients have severe permanent disability. The greatest return of muscle function occurs in the first 6 months, but improvement may continue for up to 2 years. Physical therapy is the most important part of treatment of paralytic polio during convalescence. The ideal strategy with polio is clearly to prevent it by immunization against poliovirus. U.S. President Franklin D. Roosevelt (1882-1945) had polio and worked with the National Foundation/March of Dimes to raise money to combat this once-fearsome scourge. Polio(myelitis) is also called infantile paralysis.
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An inflammatory process involving the gray matter of the cord. [polio- + G. myelos, marrow, + -itis, inflammation]
- acute anterior p. a disease that results in death or irreversible damage of motor cells in the cerebrum, brainstem, and spinal cord, caused by infection with small RNA enteroviruses of the Picornaviridae group; formerly due almost solely to one of three types of polio virus, but now more often caused by coxsackieviruses A and B, or echoviruses.
- acute bulbar p. p. virus infection affecting nerve cells in the medulla oblongata and producing paralysis of the lower motor cranial nerves.
- chronic anterior p. muscular atrophy of the upper extremities and neck, in which there are long intermissions of quiescence or improvement; not to be confused with p. virus infections.

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po·lio·my·eli·tis .pō-lē-(.)ō-.mī-ə-'līt-əs n, pl -elit·i·des -'lit-ə-.dēz an acute infectious virus disease caused by the poliovirus, characterized by fever, motor paralysis, and atrophy of skeletal muscles often with permanent disability and deformity, and marked by inflammation of nerve cells in the ventral horns of the spinal cord called also infantile paralysis, polio
po·lio·my·elit·ic -'lit-ik adj

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an infectious virus disease affecting the central nervous system. The virus is excreted in the faeces of an infected person and the disease is therefore most common where sanitation is poor. However, epidemics may occur in more hygienic conditions, where individuals have not acquired immunity to the disease during infancy. Symptoms commence 7-12 days after infection. In most cases paralysis does not occur: in abortive poliomyelitis only the throat and intestines are infected and the symptoms are those of a stomach upset or influenza; in nonparalytic poliomyelitis these symptoms are accompanied by muscle stiffness, particularly in the neck and back. Paralytic poliomyelitis is much less common. The symptoms of the milder forms of the disease are followed by weakness and eventual paralysis of the muscles: in bulbar poliomyelitis the muscles of the respiratory system are involved and breathing is affected. See also post-polio syndrome.
There is no specific treatment, apart from measures to relieve the symptoms: cases of bulbar polio may require the use of a respirator (ventilator). Immunization, using the Sabin vaccine (taken orally) or the Salk vaccine (injected), is highly effective.

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po·lio·my·eli·tis (po″le-o-mi″ə-liґtis) [polio- + myel- + -itis] an acute infectious disease occurring sporadically or in epidemics and caused by a virus, usually a poliovirus but occasionally a coxsackievirus or echovirus. It is characterized clinically by fever, sore throat, headache, and vomiting, often with stiffness of the neck and back. In the minor illness (abortive poliomyelitis) these may be the only symptoms. The major illness, which may or may not be preceded by the minor illness, is characterized by involvement of the central nervous system, stiff neck, pleocytosis in the spinal fluid, and sometimes paralysis. (See nonparalytic p. and paralytic p.) There may be subsequent atrophy of groups of muscles, ending in contraction and permanent deformity. Called also polio. The major illness is also called infantile paralysis and acute anterior p.

Medical dictionary. 2011.

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