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Polio

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Polio
SpecialtyInfectious diseases, neurology, orthopedic surgery Edit this on Wikidata

Poliomyelitis, often called polio or infantile paralysis, is a virally induced infectious disease which spreads via the fecal-oral route. It may proceed to the blood stream and into the central nervous system causing muscle weakness and often paralysis. An ancient disease, it was first recognized as a medical entity by Jakob Heine in 1840. Vaccination and eradication efforts led by the World Health Organization and The Rotary Foundation of Rotary International are credited with the reduction of the number of annual diagnosed cases from the hundreds of thousands to around a thousand.

Infection

Polio spreads through human-to-human contact, usually entering the body through the mouth due to fecally contaminated water or food (fecal-oral transmission).

The poliovirus itself is a small RNA (ribonucleic acid) virus related to Hepatitis A. There are three separate quasispecies and all are extremely infectious. While polio can strike a person at any age, over fifty percent of the cases occur in children between the ages of three and five.

The incubation period of polio, from the time of first exposure to first symptoms, ranges from three to 35 days. Most people infected with the poliovirus have no symptoms or outward signs of the illness and are thus never aware they have been infected. After initial infection with poliovirus, virus particles are excreted in the feces for several weeks. In all forms of polio, the early symptoms of infection are fatigue, fever, vomiting, headache and pain in the neck and extremities. Around 1% of unimmunized people develop paralytic complications, in some cases bulbar paralysis.

Cause of the disease

Poliovirus enters the human body through infection of the intestinal lining. From there, it penetrates into the lymphatic system via the Peyer's patches and the bloodstream via the mesentery and becomes a viremia.

In fit individuals with functioning immune systems polio infection is often subclinical, which increases the risk of contagion inasmuch as they can spread the disease through their contaminated feces unawares. Others suffer only a mild flu-like syndrome. Together these two forms of presentation account for nearly 95% of all cases of polio.

A short breakdown of the remaining cases follows:

  • 4-5% develop non-paralytic polio
  • 0.1% (children) 1.3% (adults) develop paralytic (spinal or bulbar) polio, of which:
10% die
50% recover fully
40% are left with only partial recovery (25%) or permanent paralysis (15%)

Of those 0.4% of polio patients who are left with partial recovery or permanent paralysis, the most affected locations are either one or both lower limbs. While up to 0.2% of all polio patients (1 in 500, 20% of paralytic polio cases) may require mechanical resipiration in the acute stage, permanent quadriplegia or resipiratory paralysis occur in only 0.01% (1 in 10,000) of all polio patients.

Non-paralytic polio

Non-paralytic polio may result in fever, vomiting, abdominal pain, lethargy, and irritability, and some muscles tender to the touch. In some cases there may be no significant symptoms whatsoever.

Paralytic polio

 
An iron lung ward.

The virus affects the anterior horn cells in the spinal column which control movement of the trunk and limb muscles including the intercostal muscles. An affected limb becomes floppy and poorly controlled — the condition of acute flaccid paralysis (AFP). This presentation can lead to permanent paralysis of the body yet it only occurs in around 1% of cases. The classic later appearance (as seen in ancient Egyptian illustrations) is of muscle wasting in a leg. Destroyed motor neurons do not regenerate and the affected motor units of muscles will not be able to contract. However, some sprouting from nearby surviving neurons may reinnervate the denervated muscle. This additional load on surviving motor neurons may precipitate the later developing symptoms of post-polio syndrome.

The degree of paralysis is proportional to the extent of infection of the motor nuclei, which is likely to be proportional to the degree of viraemia, and inversely proportional to the degree of immunity. Extensive paralysis of the trunk and muscles of the thorax and abdomen (quadriplegia) may occur.

Of all paralytic polio cases, 79% are spinal and 19% spinal with bulbar symptoms. If it affects the upper part of the cervical spinal cord (C3-4-5) then diaphragm paralysis requires ventilator support. Without respiratory support, polio affecting respiration is likely to result in death from failure of breathing, or aspiration of secretions and resulting pneumonia. The critical nerves are the phrenic nerve (the nerve driving the diaphragm to inflate the lungs) and the innervation to the muscles needed for swallowing. Skilled clearing of the airway with suction and tracheostomy are part of the care of such a patient, but they can expect to need mechanical ventilation. The tank respirator - iron lung - has some advantages over positive pressure applied through a tracheostomy and is still in use by a few people. In Europe, the usual treatment is either mask ventilator or tracheal ventilator. Some patients use cuirass type mechanical ventilators worn over thorax and abdomen.

Hovewer, even gravely paralyzed (quadriplegic or resipiratory paralysis) patients may recover within time. Nerves can tolerate more than 25% neurons being destroyed and maintain full muscular functionality. Only when damage exceeds to 50% neurons being destroyed, a paralysis will occur. If there are any neurons left, the remaining neurons will grow "superclustered" axons and replace those which have died. The usual recovery period is three months. Any paralysis which remain after one year is likely to be permanent, but recoveries even after a decade have been known.

Bulbar polio

Main article: Bulbar polio

The brainstem is homologous to the spinal cord, but the motor neurons arising from there and passing in the various cranial nerves control the various muscles of eyeball movements; the trigeminal nerve and facial nerve which innervate cheeks, tears, gums, and muscles of the face, etc; the glossopharyngeal nerve which in part controls swallowing and functions in the throat, tongue movement and taste; the nerve that sends signals to the heart, intestines, and lungs; and the accessory nerve that controls upper neck movement. In bulbar polio, the virus infiltrates and destroys these nerves.

The Copenhagen epidemic has been described as the start of intensive care, when large numbers of patients were ventilated by hand ("bagged") by medical students and anyone else to hand. In modern medicine, electronic ventilators have replaced bagging in long-term care situations.

The mortality rate of bulbar polio ranges from 25% to 75%,[1] according to the age of the person. If positive pressure ventilators are available, the mortality rate can be reduced to 15% [1]. In 2006 there are still polio survivors who must use a ventilator, spend their entire day or most of their day in an iron lung or attached to an assistive respiratory machine to stay alive. Bulbar polio and spinal polio are part of a continuum of anatomy and disease (paralytic polio). Bulbar polio occurs in 2% of cases of paralytic polio. Approximately one in 1000 people who have had paralytic polio have permanent resipiratory paralysis.

In extremely rare cases usually resulting from immunocompromise an uncontrolled infection of the entire brain called fulminating encephalitis can develop. Even with intravenous antiviral therapy and intensive care the mortality rate for these cases is extremely high.

Polio and children

Young children who contract polio may sometimes suffer mild symptoms, and as a result they may become permanently immune to the disease. Hence inhabitants of areas with better sanitation may actually be more susceptible to polio because fewer people have the disease as young children.

People who have survived polio sometimes develop additional symptoms, notably muscle weakness and extreme fatigue, decades later; these symptoms are called post-polio syndrome. Since it's possible to have a polio infection without having significant paralysis, many people who are unaware they ever had polio may now be suffering from post-polio syndrome.

History

The effects of a polio infection have been known since prehistory. Egyptian paintings and carvings depict otherwise healthy people with withered limbs, walking with canes at a young age, etc. It has been theorized that the Roman Emperor Claudius was stricken as a child, and this caused him to walk with a limp for the rest of his life. The first medical report on poliomyelitis was by Jakob Heine in 1840. Karl Oskar Medin was the first to empirically study a poliomyelitis epidemic in 1890. The work of these two physicians has led to the disease being known as the Heine-Medin disease.

 
Franklin D. Roosevelt may have contracted polio in 1921

Franklin D. Roosevelt may have contracted polio in 1921. The unquestioned diagnosis at the time and thereafter in countless references was paralytic poliomyelitis. Yet his age (39 years) and many features of his illness are more consistent with a diagnosis of Guillain-Barré syndrome (an autoimmune peripheral neuropathy). A peer-reviewed study published in 2003,[2] using Bayesian analysis, found that six of eight posterior probabilities favored a diagnosis of Guillain-Barré syndrome over poliomyelitis. See Franklin D. Roosevelt's paralytic illness article.

Regardless of the cause, the result was that Roosevelt was totally and permanently paralyzed from the waist down. Although the paralysis (whether from poliomyelitis or Guillain-Barré syndrome) had no cure at the time, for the rest of his life Roosevelt refused to accept that he was permanently paralyzed. He tried a wide range of therapies, but none had any effect. Nevertheless, he became convinced of the benefits of hydrotherapy, and in 1926 he bought a resort at Warm Springs, Georgia, where he founded a hydrotherapy center for the treatment of polio patients which still operates as the Roosevelt Warm Springs Institute for Rehabilitation (with an expanded mission). Furthermore, after he became President, he helped to found the National Foundation for Infantile Paralysis (now known as the March of Dimes), that supported the rehabilitation of victims of paralytic polio and the discovery of the polio vaccines.

The first iron lung was invented by Philip Drinker and demonstrated dramatic results on its first case on October 12, 1928 at Children's Hospital, Boston. The design was subsequently improved by John Haven Emerson in 1931, and the Emerson Iron Lung remains the standard to this day. The positive pressure ventilator was first time used in Blegdamshospital, Copenhagen, Denmark during a polio outbreak in 1952 [2]. It proved a success and soon superceded the tank resipirator (iron lung) all over Europe. Positive pressure ventilators reduced mortality in bulbar polio to 15%.

Vaccine history

During the late 1940's and early 1950's, a research group headed by Dr. John Enders at Boston's Children's Hospital successfuly cultivated the polio virus in human tissue. This highly significant breakthrough ultimately allowed for the development of vaccines against polio. Enders and his colleagues, Dr. Thomas H. Weller and Dr. Frederick C. Robbins, were recognized for their labors with a Nobel Prize[3] in 1954.

There were other proposed vaccines introduced before Jonas Salk's vaccine in 1953. In 1935 W. H. Park and Maurice Brody, a research assistant at New York University, claimed to have discovered a vaccine procured from ground up monkey spinal cords. Brodie tested the vaccine on himself and several of his assistants. He gave the vaccine to three thousand children and many developed allergic reactions, but no immunity to polio. Other researchers could not replicate his experiment. Philadelphia pathologist John Kolmer also claimed to have developed a vaccine that same year, and not only was that false, but it proved to be fatal to a number of children.[4]

In the 1950s, amid a U.S. polio epidemic, millions of dollars were invested in finding and marketing a polio vaccine by commercial interests, including Lederle Laboratories in New York under the direction of H. R. Cox. Polish-born virologist and immunologist Hilary Koprowski, who also worked at Lederle, claims to have created the first successful polio vaccine (in 1950) but his vaccine, a live attenuated virus taken orally, was still in the research stage and would not be ready for use until five years after Jonas Salk's polio vaccine (a dead injectable vaccine) reached the market. From a normal level of around 20,000 cases a year, the U.S. experienced an outbreak of 58,000 cases in 1952 and 35,000 in 1953. Salk's vaccine was used in a test involving 623,972 schoolchildren who received either a placebo or the vaccine. Results were announced in 1955 with the vaccine showing 80-90% efficiency. Immediate vaccination campaigns in the U.S. reduced the number of cases of polio to only 5,600 in 1957. With the addition of Sabin's vaccine after 1961, only 161 cases were recorded in the U.S. in 1964. (The last wild virus case of polio in the U.S. occurred in 1979.)

Albert Sabin used samples of difficult-to-manufacture attenuated virus given to him by Hilary Koprowski to make his own vaccine. "Koprowski would later complain that the polio vaccine he had discovered became known as the Sabin vaccine."[5][6] Koprowski's own vaccine was ultimately tested, but the outcome was a failure. After the attenuated live virus entered the body, it sometimes reverted to a virulent state.[7] Nevertheless, from 1957 to 1960, large scale tests were carried out in the Congo. The results have been controversial.[8]

The Simian Virus known as SV40 was also present in many polio vaccines from 1954 to 1962. The U.S. Food and Drug Administration and the Centers for Disease Control and Prevention have taken the lead in responding to questions on SV40 and polio vaccine. CDC states that SV40 markers have been found in certain types of human cancers, but it has not been determined if SV40 plays any role in these cancers. A recent report published by the Institute of Medicine of the National Academy of Sciences concluded that "the evidence is inadequate to accept or reject a causal relationship between SV40 containing polio vaccines and cancer." There is a need for further research to answer questions that have been raised concerning this possible relationship. More detailed information on SV40 and the polio vaccine can be found at the CDC Web site.

An analysis presented at the Vaccine Cell Substrate Conference in 2004[9] suggested that vaccines used in the former Soviet bloc countries, China, Japan, and Africa, could have been contaminated up to 1980, meaning that hundreds of millions more could have been exposed to the SV40 virus.

Vaccine-derived polio

The oral polio vaccine (Sabin or OPV) can revert to a virulent form. This is believed to be a rare event, but outbreaks of vaccine-derived poliovirus (VDPV) have been reported, and tends to occur in areas of low coverage by OPV.[10][11][12] There is currently (14 Aug 2006) an outbreak of vaccine-derived poliovirus in China.[13] This sort of polio outbreak only occurs in areas of low vaccine coverage, presumably because the OPV is itself protective against the related outbreak strain.

First effective vaccine

The first effective polio vaccine was developed by Jonas Salk at the University of Pittsburgh, although it was the oral vaccine developed by Albert Sabin eight years later that was used for modern mass inoculation. The Salk vaccine is based on formalin-inactivated poliovirus. The Sabin vaccine is a live-attenuated vaccine, produced by the passage of the virus through non-human cells at a subphysiological temperature. The first immunization of children against polio began at Arsenal Elementary School and the Watson Home for Children in Pittsburgh, Pennsylvania in 1954. Through mass immunization, the disease was wiped out in the Americas, although a small outbreak of vaccine-related polio occurred in Haiti in 2002, where political strife and poverty have interfered with vaccination efforts.[14]

Recent eradication efforts

Polio Case Counts
Year Estimated Recorded
1975 - 49,293
1980 400,000 52,552
1985 - 38,637
1988 350,000 35,251
1990 - 23,484
1993 100,000 10,487
1995 - 7,035
2000 - 2,971
2001 - 498
2002 - 1,922
2003 - 784
2004 - 1,258
2005 - 1,998
2006 - 1,763*
References:[15][16][17][18][19][20]

Due to the large increase in the number of vaccinators and field workers since 1998, the number of estimated cases is thought to be reasonably close to the actual reported number of cases in recent years.[21]

1988

In 1988, the World Health Organization passed a resolution to eradicate polio by 2000, a measure which was inspired by Rotary International's 1985 pledge to raise $120 million toward immunising all of the world's children against the disease. The next plan called for a stop of spreading the virus by 2005. Most remaining polio infections are located in two areas: the Indian sub-continent and Nigeria. Eradication efforts in the Indian sub-continent have met with a large measure of success. The Indian Government started the Pulse Polio Campaign to get rid of polio. Most families allowed their children to take the vaccine.

1994

On 20 August the Americas region was certified as polio-free.

1995

Operation Mecacar (Mediterranean, Caucasus, Central Asian Republics and Russia) is launched: from now on, National Imunnization Days are coordinated in 19 adjacent countries of the European and Mediterraenean regions of WHO.

2001

575 million children (almost one-tenth the world's population) received polio vaccine (some 2 billion doses of oral polio vaccine).

2002

The World Health Organization announces that Europe is polio-free.[22] Certification took place on June 21 in the Copenhagen Glyptotek.[23]

2003

In the Kano province in Northern Nigeria, which operates under Sharia (Muslim religious law), the immunisation campaign was suspended in September 2003 when prominent Muslim leaders said they suspected that vaccines supplied by Western donors were adulterated to reduce fertility and spread HIV as part of a U.S.-led drive against Islam.[24] On June 30, 2004, the WHO announced that Kano had pledged to restart the campaign in early July, after a 10-month ban during which the virus spread across Nigeria and into 10 other African countries that were previously polio-free. By 2006, this ban would be blamed for 1,500 children being paralyzed and having caused $450 million for emergency activities.[25]

In addition to the rumors of sterility and the ban by Nigeria's Kano state, civil war and internal strife in the countries of Sudan and Ivory Coast have complicated WHO's polio eradication goal.

  • Uttar Pradesh state in India accounted for two-thirds of the worldwide total cases reported this year.

2004

Almost two-thirds all the polio cases in the world occur in Nigeria (760 out of 1170 total).

2005

Main article: Poliomyelitis in 2005

1,831 cases of wild poliovirus (excludes vaccine derived polio viruses) were confirmed worldwide[26] with almost 40% of those occurring in Nigeria.[27]

  • India has used the Pulse Polio campaign to increase polio immunisation rates. India recorded 4,791 cases of polio in 1994, 1,600 in 2002, 225 in 2003, and 135 in 2004.[28]
  • In the United States, "On September 29 2005, the Minnesota Department of Health (MDH) identified poliovirus type 1 in an unvaccinated, immunocompromised infant girl aged 7 months (the index patient) in an Amish community whose members predominantly were unvaccinated for polio. The patient has no paralysis; the source of the patient's infection is unknown. Subsequently, poliovirus infections in three other children within the index patient's community have been documented." CDC
  • Yemen and Indonesia, neither of which had reported cases since before 2000, each had hundreds of cases - all derived from importation, probably from Nigeria.

2006

1763 cases reported by December 5, an increase from the previous year.

Only four countries in the world (Nigeria, India, Pakistan, and Afghanistan) are reported to have endemic polio. Cases in other countries are attributed to importation. Nigeria accounts for the majority of cases this year (to date) but India has reported more than ten times the number of cases this year as it had last year (30% of worldwide cases this year). Pakistan has reported 8 cases this year in children despite being given the polio medication.

Famous polio survivors

References

  1. ^ http://www.cdc.gov/nip/publications/pink/polio.pdf
  2. ^ Goldman, AS et al, What was the cause of Franklin Delano Roosevelt's paralytic illness?. J Med Biogr. 11: 232-240 (2003)
  3. ^ http://nobelprize.org/nobel_prizes/medicine/laureates/1954/
  4. ^ http://www.utexas.edu/features/2005/polio/
  5. ^ http://www.polio.info/polio-eradication/front/templates/index.jsp?codeRubrique=34&lang=EN
  6. ^ http://www.dimes.on.ca/events/iabs.asp?sect=curr
  7. ^ http://www.tufts.edu/as/wright_center/lessons/pdf/docs/activities/polio.pdf
  8. ^ http://www.koprowski.net/Polio%20Article.htm
  9. ^ http://www.newscientist.com/news/news.jsp?id=ns99996116
  10. ^ Kew OM, Morris-Glasgow V, Landaverde M; et al. (2002). "Outbreak of poliomyelitis in Hispaniola associated with circulating type 1 vaccine-derived poliovirus". Science. 296: 356–9. {{cite journal}}: Explicit use of et al. in: |author= (help)CS1 maint: multiple names: authors list (link)
  11. ^ Yang C-F, Naguib T, Yang S-J; et al. (2003). "Circulation of endemic type 2 vaccine-derived poliovirus in Egypt, 1983 to 1993". J Virol. 77: 8366–77. {{cite journal}}: Explicit use of et al. in: |author= (help)CS1 maint: multiple names: authors list (link)
  12. ^ Shimizu H, Thorley B, Paladin FJ; et al. (2004). "Circulation of type 1 vaccine-derived poliovirus in the Philippines in 2001". J Virol. 78: 13512–21. {{cite journal}}: Explicit use of et al. in: |author= (help)CS1 maint: multiple names: authors list (link)
  13. ^ Liang X, Zhang Y, Xu W; et al. (2006). "An outbreak of poliomyelitis caused by type 1 vaccine-derived poliovirus in China". J Infect Dis. 194: 545–51. {{cite journal}}: Explicit use of et al. in: |author= (help)CS1 maint: multiple names: authors list (link)
  14. ^ http://www.vaccinationnews.com/DailyNews/March2002/PolioHaitiLinkedIncompleteVax.htm
  15. ^ http://www.rotary.org/foundation/polioplus/news/eradication.html
  16. ^ http://www.rotary.org/foundation/polioplus/news/milestones/index.html
  17. ^ http://www.polioeradication.org/casecount.asp
  18. ^ http://www.who.int/vaccines/immunization_monitoring/en/diseases/poliomyelitis/afpextract.cfm
  19. ^ http://www.unicef.org/pon95/heal0002.html
  20. ^ http://www.worldwatch.org/node/1644
  21. ^ http://www.who.int/bulletin/volumes/83/4/268.pdf#search=%222005%20%22%20estimated%20polio%20cases%22%22
  22. ^ http://www.europaworld.org/week88/unhealthbody28602.htm
  23. ^ http://www.euro.who.int/mediacentre/PR/2002/20020620_1
  24. ^ http://allafrica.com/stories/200407020367.html
  25. ^ http://news.yahoo.com/s/ap/20061012/ap_on_he_me/un_polio_who;_ylt=ApbHVMLfLg1C8MIDSa80lxIR.3QA;_ylu=X3oDMTA3czJjNGZoBHNlYwM3NTE-
  26. ^ http://www.polioeradication.org/content/fixed/casemap.shtml
  27. ^ http://www.polioeradication.org/casecount.asp
  28. ^ http://onlypunjab.com/fullstory2k5-insight--status-22-newsID-25278.html
 
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Further reading

  • Maus, Richard A. (2006). Lucky One: Making it Past Polio and Despair. Anterior Publishing. ISBN 0-9776205-0-6. (A memoir by a childhood survivor of polio.)
  • Paul, John R. (1971). A History of Poliomyelitis. Yale University Press. (Classic history.)
  • Wilson, Daniel J. (2005). Living with Polio: The Epidemic and Its Survivors. University of Chicago Press. (History of polio from accounts written by survivors.)
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