What is Polio?
Polio or Poliomyelitis or Infantile Paralysis is an infectious disease caused by a virus called Poliovirus that mostly affects children but may occur in unvaccinated adults. The poliovirus can damage cells in the nervous system leading to paralysis but this only occurs in about 2% of those infected with it. Children are mostly affected and are more at risk; because the disease could cause paralysis right from infancy (hence the name: Infantile Paralysis). The word Poliomyelitis is derived from the Greek word polio (which means grey) and myelon (which means marrow – indicating the spinal cord).
There is a probable case of Polio if there is an acute onset of a flaccid paralysis of one or more limbs with decreased or absent tendon reflexes in the affected limbs, without other apparent cause, and without sensory or cognitive loss.
There is a confirmed case of Polio when there is an acute onset of a flaccid paralysis of one or more limbs with decreased or absent tendon reflexes in the affected limbs, without other apparent cause, and without sensory or cognitive loss AND in which the patient has a neurologic deficit 60 days after onset of initial symptoms, or the patient has died, or has unknown follow-up status.
Cause of Polio
Poliomyelitis is caused by three different strains of Viruses named after the disease: Poliovirus types 1, 2 and 3. Poliovirus type 1 causes the paralysis the most and it is frequently the cause of paralytic polio epidemics. The virus is a member of the Picornaviridae family and it is an RNA virus.
How do you get Polio? (Polio Transmission)
Transmission of Polio occurs through the feco-oral route, that is, babies get infected when they eat food contaminated with feces from an infected person. An infected person can transmit the virus about 7 to 10 days before the symptoms even begin to manifest because once the symptoms manifest, the person will not be infective again. The virus when excreted in stool remains infective for 3 to 6 weeks. Humans are the reservoirs for the virus which means that the virus is picked from an infected person to another person.
Although Polio (poliomyelitis) mainly affects children especially those under the age of 5, it can affect adults who have not been vaccinated. Not all cases of Polio lead to paralysis but a few (about 1 in 200 cases of polio leads to paralysis). Out of the few who become paralyzed with polio, about 5% to 10% die due to the paralysis of the muscles of the chest that are used for breathing.
There has been drastic reduction in the cases of Polio due to the aggressive global efforts to eradicate Polio (as of 1988, there were 125 countries that were polio-endemic); as of 2012, only three countries: Afghanistan, Pakistan and Nigeria were polio-endemic; with Nigeria being declared Polio free in 2015 but in 2016 other cases of Polio when found in the Northern part of the country. A single case of Polio qualifies a country as Polio endemic because that single case may spread to other children because they are at risk.
Infection with poliovirus occurs through the mouth; the poliovirus then replicates in the pharynx, gastrointestinal tract and local lymphatics. It is then spread to the central nervous system (CNS) and lymphatics by hematologic route. The poliovirus has a high propensity towards the anterior horn cells of the spinal cord, especially those within the lumbar region causing lower motor neuron (flaccid) paralysis of the affected muscle groups. It gains entry into the CNS by retrograde axonal transport, or transport across blood brain barrier or transport via infected macrophages which helps the virus to evade immune detection. The nerve cells affected do not regenerate again this is the reason why there is irreversible paralysis; sometimes axonal sprouting may result in some recovery of function.
Polio Symptoms and Signs
Polio symptoms occur in phases depending on the stage of the disease. In most cases of Polio (in 95% of those infected) there is no symptom. In the remaining percentage of those who present with symptoms, the symptoms are dependent on the phase of the disease. Polio has an incubation period of 7 to 14 days.
- The acute illness phase (or Abortive Poliomyelitis): this occurs in about 4 to 5% of cases. This is self-limiting and has a short duration
- Non-paralytic poliomyelitis (causing poliovirus meningitis): this also has the symptoms of abortive poliomyelitis as well as signs of meningeal irritation, but recovery in this case is complete
- Phase of Paralysis (Paralytic poliomyelitis): this occurs in about 0.1% of infected children and in 1.3% of infected adults. There are certain risk factors that predispose to having paralysis in Polio (see risk factors below)
- Phase of Recovery and convalescence
- Phase of Residual paralysis
- Post-polio syndrome
Abortive Polio Symptoms (Phase of Acute illness)
- Sore throat
- Neck stiffness
- Patient lies with flexed joints
- Tender and painful muscles, including painful muscle spasm on mild stretching
Symptoms of Paralytic phase of Polio
- Progressive muscle weakness leading to complete irreversible muscle paralysis within 3 days from start of the muscle weakness
- When the respiratory muscles are affected, there will be difficulty in breathing and swallowing. This also leads to complete paralysis of respiratory muscles and the patient is unable to breath (this is a cause of death in Polio). When there is no involvement of respiratory muscles, no breathing is affected and death is unlikely.
- The fever and muscle pain subside after 7 to 10 days (An infected person can infect others with polio only within the first 4 weeks of being infected)
Paralytic Polio Risk Factors
- Older age
- Male gender
- Being unvaccinated or inadequate vaccination stills put you at risk of having Polio
- Lower socioeconomic status
- Associated co-infection
- Strenuous exercise
- Surgery such as tonsillectomy, trauma, or pregnancy
3 different types of Paralytic polio
- Spinal paralytic polio
- Bulbar polio
Phase of Recovery and convalescence in Polio
In this phase, a gradual return of muscle power is noticed and this occurs over a period of 6 months and sometimes, there will be more improvement up to 2 years.
Signs of Residual paralysis Phase in Polio
- In this phase, some patients may experience full muscle recovery
- In others, full muscle paralysis does not occur and are left with asymmetric flaccid paralysis or unbalanced muscle weakness which causes joint deformities and growth defects
Deformities of Poliomyelitis
- Deformities caused by Polio include Scoliosis
- Weakness of hamstring muscles
- Pelvic obliquity
- Flail knee
- Fixed flexion deformity at the knee
- Equinus at the ankle
- Limb shortening from poor bone growth because of absent muscle stimulation
- Post-polio syndrome may occur (Post-polio syndrome is the reactivation of poliovirus that causes muscle weakness in muscles that were previously affected in the initial infection or in new muscle groups)
- In early stage of Polio, the Polymorphonuclear leukocytes in the cerebrospinal fluid (CSF) increase which are then replaced after 2 to 3 days with moderate numbers of lymphocytes and monocytes
- The CSF protein is elevated only slightly; in the case of paralytic polio, the CSF rises gradually up to the 3 week and then returns to its normal value by the 6th week.
- The CSF glucose levels are normal
- Confirmatory test can be done by culture of the Poliovirus from stool samples (2 stool samples are collected 24-48 hours apart) or from CSF sample
Early treatment of Polio is basically supportive and late cases require physiotherapy. Treatment may require ventilatory support when the respiratory muscles are affected.
Early phase treatment of Polio
- Early treatment involves complete bed rest and isolation of patient ed and kept at complete rest
- Analgesics and muscle relaxants are given to treat pain and muscle spasms
- Respiratory paralysis will require artificial respiration with a ventilator
- If the acute illness is over, commence physiotherapy immediately to prevent deformities and help in maintaining Limb alignment. This is done by splinting of joints between exercise periods
Late phase treatment of Polio
When the severity of the residual paralysis is established, the aim of treatment is to improve the functionality of affected limbs, stabilization of flail joints and balancing activity of muscles about a joint. The established deformities are then corrected and further deformity prevented.
Measures for treatment in the Late phase of Polio
- Tendon transfers where muscle imbalance occurs about a joint
- Splinting the limbs
- Use of orthosis such as knee, ankle or foot orthosis
- Arthrodesis of flail joints (surgical immobilization of the joints)
- Surgical realignment of fixed deformities
Differential Diagnosis of Poliomyelitis
- Other non-polio enteroviruses such as Coxsackie viruses A and B, Echovirus and Enterovirus 70 and 71
- Guillain Barre Syndrome
- Acute Traumatic sciatic neuritis
- Acute transverse myelitis
- Myasthenia gravis
Mortality rate of Polio is about 10.15% but may be as high as 15.40% in some epidemics. About 15 to 40% have residual paralysis.
- Vaccination of children against Polio (use of inactivated polio vaccine, IPV and oral polio vaccine, OPV)
- Aggressive enlightenment campaigns especially to people or groups who decline vaccinations for religious or cultural believes
- Early notification of any case of Polio
- Isolation to prevent transmission to others
- Surveillance of acute flaccid paralysis
- Good personal hygiene and food hygiene should be encouraged and practised
- Safe disposal of faeces
Complications of Polio
- Abnormal gait
- Aspiration pneumonia
- Paralytic ileus
- Urinary calculi
- Death due to respiratory muscle paralysis
- One of the notable persons who had Polio was the President of the United States of America, President Franklin Roosevelt he committed funds to a war on polio.
- The Inactivated Polio Vaccine (IPV) was developed by Jonas Salk and was named after him as Salk Vaccine (it is a killed vaccine)
- The Oral Polio Vaccine was developed by Albert B. Sabin and is also named after him as Sabin Vaccine (it is an attenuated vaccine)
- There is currently no cure for Poliomyelitis
- 24th of October is the World Polio Day
- The Global Polio Eradication Initiative was launched in 1988 during the 41st World Health Assembly
- Polio had existed over 3,000 years ago but was first described in Britain in 1789 by Michael Underwood when outbreaks in children were occurring
- Polio epidemics occurred frequently until the discovery of the polio vaccine in the 1950s and Children were most at risk, with some suffering muscle damage that was severe enough to require the assistance of iron lungs (which were early mechanical ventilators, as a result of their lungs being damaged to the point of incapacity).