2/12/2014

Polio is caused by a human enterovirus called the poliovirus. Wild polioviruses are those that occur naturally.

The virus

Polio is caused by a human enterovirus called the poliovirus. Wild polioviruses are those that occur naturally.

The poliovirus consists of an RNA genome enclosed in a protein shell called a capsid. There are three serotypes of wild poliovirus – type 1, type 2, and type 3 – each with a slightly different capsid protein.
Scanning electron micrograph of the wild poliovirus
The wild poliovirus as seen through a microscope. The virus invades the nervous system, causing paralysis in one out of every 200 children.
From GPEI site photo gallery
Type 2 poliovirus has been eliminated in the wild – the last wild type 2 poliovirus was detected in India in 1999. 
In this final stage of polio eradication, only type 1 and type 3 wild poliovirus continue to circulate in endemic areas. Both are highly infectious and both cause paralytic polio. Type 1 is the most pervasive strain of poliovirus, with type 3 highly localized in northern India, northern Nigeria, Pakistan and Afghanistan.






Polio and prevention
Polio is a crippling and potentially fatal infectious disease. There is no cure, but there are safe and effective vaccines. The strategy to eradicate polio is therefore based on preventing infection by immunizing every child until transmission stops and the world is polio-free.
The disease
Polio (poliomyelitis) is a highly infectious disease caused by a virus. It invades the nervous system and can cause irreversible paralysis in a matter of hours.
Indian boy with polio
An Indian boy’s legs are shrunken from paralysis caused by polio
WHO/T. Moran

Who is at risk?

Polio can strike at any age, but it mainly affects children under five years old.

Transmission

Polio is spread through person-to-person contact. When a child is infected with wild poliovirus, the virus enters the body through the mouth and multiplies in the intestine. It is then shed into the environment through the faeces where it can spread rapidly through a community, especially in situations of poor hygiene and sanitation. If a sufficient number of children are fully immunized against polio, the virus is unable to find susceptible children to infect, and dies out.

Young children who are not yet toilet-trained are a ready source of transmission, regardless of their environment. Polio can be spread when food or drink is contaminated by faeces. There is also evidence that flies can passively transfer poliovirus from faeces to food.

Most people infected with the poliovirus have no signs of illness and are never aware they have been infected. These symptomless people carry the virus in their intestines and can “silently” spread the infection to thousands of others before the first case of polio paralysis emerges.

For this reason, WHO considers a single confirmed case of polio paralysis to be evidence of an epidemic – particularly in countries where very few cases occur.

Symptoms

Most infected people (90%) have no symptoms or very mild symptoms and usually go unrecognized. In others, initial symptoms include fever, fatigue, headache, vomiting, stiffness in the neck and pain in the limbs.

Acute flaccid paralysis (AFP)

One in 200 infections leads to irreversible paralysis, usually in the legs. This is caused by the virus entering the blood stream and invading the central nervous system. As it multiplies, the virus destroys the nerve cells that activate muscles. The affected muscles are no longer functional and the limb becomes floppy and lifeless – a condition known as acute flaccid paralysis (AFP).

All cases of acute flaccid paralysis (AFP) among children under fifteen years of age are reported and tested for poliovirus within 48 hours of onset.

Bulbar polio

More extensive paralysis, involving the trunk and muscles of the thorax and abdomen, can result in quadriplegia. In the most severe cases (bulbar polio), poliovirus attacks the nerve cells of the brain stem, reducing breathing capacity and causing difficulty in swallowing and speaking. Among those paralysed, 5% to 10% die when their breathing muscles become immobilized.
In the 1940s and 1950s, people with bulbar polio were immobilized inside "iron lungs" – huge metal cylinders that operated like a pair of bellows to regulate their breathing and keep them alive. Today, the iron lung has largely been replaced by the positive pressure ventilator, but it is still in use in some countries.

Post-polio syndrome

Around 40% of people who survive paralytic polio may develop additional symptoms 15–40 years after the original illness. These symptoms – called post-polio syndrome – include new progressive muscle weakness, severe fatigue and pain in the muscles and joints.

Risk factors for paralysis

No one knows why only a small percentage of infections lead to paralysis. Several key risk factors have been identified as increasing the likelihood of paralysis in a person infected with polio. These include:
  • immune deficiency
  • pregnancy
  • removal of the tonsils (tonsillectomy)
  • intramuscular injections, e.g. medications
  • strenuous exercise
  • injury.

    Treatment and prevention

    There is no cure for polio, only treatment to alleviate the symptoms.  Heat and physical therapy is used to stimulate the muscles and antispasmodic drugs are given to relax the muscles. While this can improve mobility, it cannot reverse permanent polio paralysis.

    Polio can be prevented through immunization. Polio vaccine, given multiple times, almost always protects a child for life.
    Related links

    History of polio

    In the early 20th century, polio was one of the most feared diseases in industrialized countries, paralysing thousands of children every year. Soon after the introduction of effective vaccines in the 1950s and 1960s however, polio was brought under control and practically eliminated as a public health problem in these countries.

    It took somewhat longer for polio to be recognized as a major problem in developing countries. Lameness surveys during the 1970s revealed that the disease was also prevalent in developing countries. As a result, during the 1970s routine immunization was introduced worldwide as part of national immunization programmes, helping to control the disease in many developing countries.

    In 1988, when the Global Polio Eradication Initiative began, polio paralysed more than 1000 children worldwide every day. Since then, 2.5 billion children have been immunized against polio thanks to the cooperation of more than 200 countries and 20 million volunteers, backed by an international investment of more than US$ 8 billion.

    Today, polio has been eliminated from most of the world and only four countries remain endemic. In 2009, fewer than 2000 cases were reported for the entire year.

    Use this interactive timeline to trace the history of polio from 1580 B.C. to the present.


    http://www.polioeradication.org/Polioandprevention/Historyofpolio.aspx



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    Post Polio Litaff, Association A.C _APPLAC Mexico

    The Polio Crusade

    THE POLIO CRUSADE IN AMERICAN EXPERIENCE A GOOD VIDEO THE STORY OF THE POLIO CRUSADE pays tribute to a time when Americans banded together to conquer a terrible disease. The medical breakthrough saved countless lives and had a pervasive impact on American philanthropy that ... Continue reading..http://www.pbs.org/wgbh/americanexperience/polio/

    Erradicación de La poliomielitis

    Polio Tricisilla Adaptada

    March Of Dimes Polio History

    Dr. Bruno

    video

    movie

    movie2

    A 41-year-old man developed an acute illness at the age of 9 months during which, following a viral illness with headache, he developed severe weakness and wasting of the limbs of the left side. After several months he began to recover, such that he was able to walk at the age of 2 years and later was able to run, although he was never very good at sports. He had stable function until the age of 18 when he began to notice greater than usual difficulty lifting heavy objects. By the age of 25 he was noticing progressive difficulty walking due to weakness of both legs, and he noticed that the right calf had become larger. The symptoms became more noticeable over the course of the next 10 years and ultimately both upper as well as both lower limbs had become noticeably weaker.

    On examination there was wasting of the muscles of upper and lower limbs on the left, and massively hypertrophied gastrocnemius, soleus and tensor fascia late on the right. The calf circumference on the right exceeded that on the left by 10 cm (figure1). The right shoulder girdle, triceps, thenar eminence and small muscles of the hand were wasted and there was winging of both scapulae. The right quadriceps was also wasted. The wasted muscles were also weak but the hypertrophied right ankle plantar flexors had normal power. The tendon reflexes were absent in the lower limbs and present in the upper limbs, although the right triceps was reduced. The remainder of the examination was normal.

    Figure 1

    The patient's legs, showing massive enlargement of the right calf and wasting on the left

    Questions

    1
    What is that nature of the acute illness in infancy?
    2
    What is the nature of the subsequent deterioration?
    3
    What investigations should be performed?
    4
    What is the differential diagnosis of the cause of the progressive calf hypertrophy?

    Answers

    QUESTION 1

    An acute paralytic illness which follows symptoms of a viral infection with or without signs of meningitis is typical of poliomyelitis. Usually caused by one of the three polio viruses, it may also occur following vaccination and following infections with other enteroviruses.1 Other disorders which would cause a similar syndrome but with upper motor neurone signs would include acute vascular lesions, meningoencephalitis and acute disseminated encephalomyelitis.

    QUESTION 2

    A progressive functional deterioration many years after paralytic poliomyelitis is well known, although its pathogenesis is not fully understood.2 It is a diagnosis of exclusion; a careful search for alternative causes, for example, orthopaedic deformities such as osteoarthritis or worsening scoliosis, superimposed neurological disorders such as entrapment neuropathies or coincidental muscle disease or neuropathy, and general medical causes such as respiratory complications and endocrinopathies.3

    QUESTION 3

    Investigations revealed normal blood count and erythrocyte sedimentation rate and normal biochemistry apart from a raised creatine kinase at 330 IU/l (normal range 60–120 IU/l), which is commonly seen in cases of ongoing denervation. Electromyography showed evidence of denervation in the right APB and FDI with polyphasic motor units and complex repetitive discharges, no spontaneous activity in the left calf and large polyphasic units in the right calf consistent with chronic partial denervation. Motor and sensory conduction velocities were normal. A lumbar myelogram was normal. Magnetic resonance imaging (MRI) scan of the calves is shown in figure2.

    Figure 2

    Axial T1 weighted MRI scan (TR 588 ms, TE 15 ms) of the calves, showing gross muscle atrophy and replacement by adipose tissue on the left, and hypertrophy of the muscles on the right, with only minor adipose tissue deposition

    QUESTION 4

    The differential diagnosis of the progressive calf hypertrophy is given in the box.

    Causes of calf muscle hypertrophy

    Chronic partial denervation

    • radiculopathy

    • peripheral neuropathy

    • hereditary motor and sensory neuropathy

    • spinal muscular atrophy

    • following paralytic poliomyelitis

      Neuromyotonia and myokymia

    • Isaac's syndrome

    • generalised myokymia

    • neurotonia

    • continuous muscle fibre activity due to: chronic inflammatory demyelinating polyradiculopathy, Guillain Barre syndrome, myasthenia gravis, thymoma, thyrotoxicosis, thyroiditis

      Muscular dystrophies

      Myositis

      Infiltration

    • tumours

    • amyloidosis

    • cysticercosis

      Link here