Poliomyelitis

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Poliomyelitis, often called polio or infantile paralysis, is a viral paralytic disease. The causative agent, a virus called poliovirus (PV), enters the body orally, infecting the intestinal wall. 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. Eradication efforts led by the World Health Organization and The Rotary Foundation of Rotary International have reduced the number of annual diagnosed cases from the hundreds of thousands to around a thousand.

Infection

Polio is a communicable disease which is categorized as a disease of civilization. Polio spreads through human-to-human contact, usually entering the body through the mouth due to fecally contaminated water or food. The poliovirus is a small RNA (ribonucleic acid) virus that has three different strains and is extremely infectious. The virus invades the nervous system, and the onset of paralysis can occur in a matter of hours. 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 thirty five days, thus Polio can spread widely before a polio outbreak is apparent. 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 faeces for several weeks and are highly transmissible to others in a community. 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 unimmunised people develop paralytic complications, in some cases bulbar paralysis.

The Course of the Disease

Initial infection is of cells in the lining of the small intestine. Immunization interrupts the process here. After multiplication there, viraemia occurs, with distribution of virus to other parts of the body. Flu-like symptoms are typical of viraemia from any cause. The virus has an affinity for the cell bodies of motor neurones, which carry commands to the muscles.

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.

Spinal polio

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 but usually (> 99% of cases)Template:Fact does not. 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.

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 cranial 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.

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. Thus, bulbar polio could affect any or all of these functions.

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. Nowadays electricity drives them.

The mortality rate of bulbar polio ranges from twenty-five to seventy-five percent [1], according to the age of the person. In 2006 there are still polio survivors who must 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).

Fulminating encephalitis (an overwhelming invasion of the virus into other parts of the brain) is rare, but is most often lethal.

Polio and children

Young children who contract polio may sometimes suffer only 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. United States president Franklin D. Roosevelt contracted polio in 1921 and was paralyzed from the waist down as a result. 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. Image:Rooseveltinwheelchair.jpg

Failures and scandals

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 several children [2].

In the 1950s 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. Albert Sabin used samples of difficult to manufacture attenuated virus given to him by Hilary Koprowski to make his own version. "Koprowski would later complain that the polio vaccine he had discovered became known as the Sabin vaccine." [3] [4] 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 [5]. Nevertheless, from 1957 to 1960, large scale tests were carried out in the Congo. The results have been controversial [6].

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 [7] 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 virus.

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 immunisation 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 it recently has re-appeared in Haiti, where political strife and poverty have interfered with vaccination efforts. [8]

Recent eradication efforts

Number of cases [9] [10] [11] [12]:

• 1988: 350,000
• 1996: 4,074
• 1997: 5,185
• 1998: 6,349
• 1999: 7,141
• 2000: 2,971
• 2001: 498
• 2002: 1,922
• 2003: 784
• 2004: 1,258
• 2005: 1,998

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. Some Muslim families refused due to false rumors that the vaccine causes impotence or infertility or both.

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. [13] 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.

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.

2005

1,831 cases of wild poliovirus (excludes vaccine derived polio viruses [14]).

727 Nigeria (endemic)
478 Yemen  (importation)
299  Indonesia (importation)
154 Somalia (importation)
64 India (endemic)
27 Pakistan (endemic)
27 Sudan (re-established transmission)
20 Ethiopia (importation) 
9 Angola (importation)
9 Niger (endemic)
7 Afghanistan (endemic)
4 Nepal (importation)
3  Mali (importation)
1 Chad (re-established transmission)
1  Eritrea (importation)
1 Cameroon (importation)

Source: Polio cases from 1 January 2005, as of 17 January 2006

• Nigeria: "Fifty-four new polio cases were recorded in Nigeria between February and April, a drop of nearly a half from last year, according to the World Health Organisation. The infection rate is down from the 91 cases recorded between 27 February and 29 April 2004, WHO said in its weekly report obtained on Thursday. The report said nine new cases were confirmed in Yobe state and Nigeria's biggest city, Lagos—the first in the southern region where WHO said there had been no fresh infections since September. WHO said improved control in the southern states and resumed immunisation in the north, where Muslim clerics led a boycott of vaccination in late 2003, explained the drop in new infections." [15]
• Sudan: "Since the beginning of 2005, the ICRC's various primary health clinics have managed to immunise more than 99,000 children under five years of age against poliomyelitis. In all, 78,654 children were immunised in Darfur (Seleia, Zalingei, Kutum and Gereida) and 20,432 in southern Sudan (Yirol and Chelkou). The first case of the polio outbreak in Sudan was detected in May 2004. Since then, health organizations have registered cases in 17 of the 26 states of the country. The Sudanese health authorities have intensified the national immunisation campaign and the ICRC has provided its support, particularly in conflict-affected regions." [16]
• Yemen: "More than 40 new cases of polio have been confirmed in Yemen, the World Health Organization said yesterday, more new cases than in any other nation. ... Epidemiologists expect the 63 cases confirmed thus far in Yemen, a poor country on the southern tip of the Arabian peninsula, to grow to more than 100 soon." nytimes 2005/05/11
• India: 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. [17]
• Pakistan: "In 2003, we had around 103 reported cases of polio, which dropped by almost 50 percent in 2004 with a total of 53 cases registered. Now, so far in 2005, a total of only five polio cases have been reported, Jeffery Bates, polio communications officer at the United Nations Children's Fund (UNICEF) told IRIN on Thursday, the concluding day of the national polio immunisation campaign." [18]
• Indonesia: On May 5 2005, news reports broke that a new case of polio was diagnosed in Java, Indonesia and the virus strain was suspected to be the same as the one that caused the outbreak in Nigeria. [19][20]. New public fears over vaccine safety, which were unfounded, impeded vaccination efforts. In summer 2005 the WHO, UNICEF and the Indonesian government made new efforts to lay the fears to rest, recruiting celebrities and religious leaders in a publicity campaign.[21]
• 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

2006

Polio cases for 2006 [22]:

Nigeria (endemic) 65
India (endemic) 16
Somalia (importation) 14
Afghanistan (endemic) 3
Niger (importation) 3
Pakistan (endemic) 2
Indonesia (importation) 1
Ethiopia (importation) 1
Bangladesh (importation) 1
Yemen (importation) 1

Social impact

In Benin, where some families reject vaccination on religious grounds, polio victims are informally tolerated to smuggle petrol from neighbouring Nigeria. The polio survivors ride their motor tricycles to the border, with the company of a mechanic that takes care of the machine and the rider.

In Nigeria, they fill whatever receptacles they can carry and ride back. In spite of the illegality of the trade and the safety risk of moving around petrol in bottles, they are tolerated by the customs officers and the Beninese society. The polio victims have in their daily trips (one or two) a means of life with more dignity than begging, and that involves them in the community life instead of being outcasts.

External links

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• Global Polio Eradication
• Rotary International: PolioPlus
• University of Pittsburgh's Jonas Salk and Polio information
• Pittsburgh Post-Gazette on 50 years of Polio
• Elimination of Polio in Latin America and the Caribbean
• Audio and text about Franklin D. Roosevelt's granddaughter expressing hope for rapid eradication of polio.

Further reading

• Template:Cite book (Awarded the 2006 Pulitzer Prize for history.)da:Polio

de:Kinderlähmung es:Poliomielitis eo:Poliomjelito fr:Poliomyélite ko:소아마비 io:Poliomielito id:Polio it:Poliomielite he:שיתוק ילדים nl:Poliomyelitis ja:急性灰白髄炎 no:Poliomyelitt pl:Choroba Heinego-Medina pt:Poliomielite ru:Полиомиелит su:Polio fi:Polio sv:Polio uk:Поліомієліт zh:小兒麻痺