The term “poliomyelitis” is used to identify the disease caused by any of the three serotypes of poliovirus. Two basic patterns of polio infection are described: a minor illness which does not involve the central nervous system (CNS), sometimes called abortive poliomyelitis, and a major illness involving the CNS, which may be paralytic or nonparalytic.[12]In most people with a normal immune system, a poliovirus infection is asymptomatic. Rarely, the infection produces minor symptoms; these may include upper respiratory tract infection (sore throat and fever), gastrointestinal disturbances (nausea, vomiting, abdominal pain, constipation or, rarely, diarrhea), and influenza-like illness.[1]
The virus enters the central nervous system in about 1% of infections. Most patients with CNS involvement develop nonparalytic aseptic meningitis, with symptoms of headache, neck, back, abdominal and extremity pain, fever, vomiting,lethargy, and irritability.[13][14] About one to five in 1000 cases progress to paralytic disease, in which the muscles become weak, floppy and poorly controlled, and, finally, completely paralyzed; this condition is known as acute flaccid paralysis.[15] Depending on the site of paralysis, paralytic poliomyelitis is classified as spinal, bulbar, or bulbospinal.Encephalitis, an infection of the brain tissue itself, can occur in rare cases, and is usually restricted to infants. It is characterized by confusion, changes in mental status, headaches, fever, and, less commonly, seizures and spastic paralysis.[16]
Cause
A TEM micrograph of poliovirus
Poliomyelitis is caused by infection with a member of the genus Enterovirus known as poliovirus (PV). This group of RNA viruses colonize the gastrointestinal tract[17] — specifically the oropharynx and the intestine. The incubation time (to the first signs and symptoms) ranges from three to 35 days, with a more common span of six to 20 days.[1] PV infects and causes disease in humans alone.[18] Its structure is very simple, composed of a single (+) sense RNA genome enclosed in a protein shell called a capsid.[18] In addition to protecting the virus’s genetic material, the capsid proteins enable poliovirus to infect certain types of cells. Three serotypes of poliovirus have been identified—poliovirus type 1 (PV1), type 2 (PV2), and type 3 (PV3)—each with a slightly different capsid protein.[19] All three are extremely virulent and produce the same disease symptoms.[18] PV1 is the most commonly encountered form, and the one most closely associated with paralysis.[20]
Individuals who are exposed to the virus, either through infection or by immunization with polio vaccine, develop immunity. In immune individuals, IgA antibodies against poliovirus are present in the tonsils and gastrointestinal tract, and are able to block virus replication; IgG and IgM antibodies against PV can prevent the spread of the virus to motor neurons of the central nervous system.[21] Infection or vaccination with one serotype of poliovirus does not provide immunity against the other serotypes, and full immunity requires exposure to each serotype.[21]
A rare condition with a similar presentation, nonpoliovirus poliomyelitis, may result from infections with nonpoliovirusenteroviruses.[22]
Source: Wiki
Treatment
- General: There is no cure for polio. The goal of treatment is to control symptoms and to prevent complications. Some forms of polio require no treatment. However, severe forms may require orthopedic surgery. Common treatments include physical therapy, braces, and corrective shoes. Antiviral drugs are being studied for effectiveness against poliovirus; however, further research in this area is needed.
- Antibiotics: Antibiotics are not effective against the polio virus itself but may be prescribed in patients that have coexisting infections, such as a urinary tract infection.
- Bethanechol: Bethanechol may be used in polio patients who experience urinary retention.
- Braces or corrective shoes: In cases of paralytic polio, leg braces and corrective shoes may be used to assist in proper walking. Patients who wear braces should also participate in physical therapy to prevent muscle damage associated with a lack of use.
- Lifestyle changes: Bed rest may be advised for patients with severe forms of polio.
- Moist heat: The use of heating pads and warm towels may be advised in patients with polio who experience muscle pain and spasms.
- Nutritional changes: A nutritious diet is critical for patients with polio, to give the body all the resources that it needs to fight off the infection.
- Painkillers: Painkillers may be given to manage symptoms, including headache, muscle pain, and muscle spasms. Narcotics are usually avoided due to an increased risk of breathing difficulties.
- Physical therapy: Patients with paralytic polio may benefit from moderate exercise to prevent deformity and loss of muscle function. Swimming may benefit patients who experience pain and muscle weakness.
- Portable ventilators: Jacket-type negative-pressure ventilators worn over the chest and abdomen assist patients with polio who are not able to breathe unassisted. In some cases, ventilator use may be temporary, although some patients may need to use them for the rest of their lives.
- Surgery: In severe polio cases, orthopedic surgery may be performed to help recover muscle strength and function.
- Treatments for post-polio syndrome: Post-polio syndrome may occur decades after a polio infection has run its course. Treatments available for patients with post-polio syndrome include pyridostigmine, immunoglobulin, coenzyme Q10, and physical therapy.