Poliomyelitis ("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.

Eradication efforts led by the World Health Organization have reduced the number of annual diagnosed cases from the hundreds of thousands to around a thousand.

Infection

Polio (infantile paralysis) 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 occurred to 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.

Polio can spread widely before physicians detect the first signs of a polio outbreak. Surprisingly, 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 the person is exposed to the poliovirus, the virus is expelled through faeces for several weeks and it is during this time that a polio outbreak can occur in a community. The three strains of poliovirus result in non-paralytic polio, paralytic polio, and bulbar polio. In all forms of polio, the early symptoms of infection are fatigue, fever, vomiting, headache and pain in the neck and extremities.

Types of polio

Non-paralytic polio

Non-paralytic polio will result in fever, vomiting, abdominal pain, lethargy, and irritability. Some muscle spasms in the neck and back, with muscles generally tender to the touch.

Spinal paralytic polio

This strain of the poliovirus attacks the spinal column where it destroys the anterior horn cells which control movement of the trunk and limb muscles. Although this strain of the poliovirus can lead to permanent paralysis, less than one in two hundred with symptoms will result in paralysis. The most common paralysis will affect the legs. Once the poliovirus invades the intestines, it is absorbed by the capillaries in the walls of the intestine and is then carried by the bloodstream throughout the body. The poliovirus attacks the spinal column and the motor neurons—which control physical movement. It is during this period of infection that flu-like symptoms occur; however, for people who have no immunity or have not been vaccinated, the virus usually goes on to infect the entire spinal column and the brain stem. This infection affects the central nervous system (CNS)—spreading along nerve fibers. As the virus continues to multiply in the CNS, the virus destroys motor neurons. Motor neurons do not regenerate and any affected muscles will no longer respond to CNS commands. The most common paralysis occurs to the muscles of the legs. The result is that the limb becomes floppy and lifeless—a condition known as acute flaccid paralysis (AFP). An extreme infection of the CNS can cause extensive paralysis of the trunk and muscles of the thorax and abdomen (quadriplegia).

Bulbar polio

Bulbar polio is thought to be the result of a person having no natural resistance to the polio virus, the result being that the brain stem is allowed to be attacked. The brain stem contains the motor neurons that control breathing and the cranial nerves, which signal the various muscles that control eyeball movements; the trigeminal nerve and facial nerve which innervate cheeks, tears, gums, and muscles of the face, etc; the auditory nerve which provides hearing; 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.

Without respiratory support, bulbar polio usually results in death. Of those who become infected, five to ten percent will die when their breathing muscles become immobilized. Death usually occurs after damage to the cranial nerve responsible for sending the signal to breathe to the lungs. Bulbar victims may also die from damage to the swallowing function; a victim can drown in their own secretions unless adequately suctioned, or given a tracheostomy to suction secretions before the liquid enters the lungs. It is difficult to have a tracheostomy and still be able to tolerate the airtight collar of an iron lung. There may also be an overwhelming invasion of the virus into other parts of the brain causing coma and death.

The mortality rate of bulbar polio ranges from twenty-five to seventy-five percent, with the variable being the age of the person. To this day 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 often coexist. They are both a subclass of paralytic polio. Paralytic polio is not necessarily permanent. One can have had paralytic polio and recover seemingly normal function.

Polio and children

Young children who contract polio are likely to 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.

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 first inoculations 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. [1]

Eradication efforts

Number of cases [2] [3] [4]:

• 1988: 350,000
• 1999: 7,083
• 2004: 1,300
• 2005: 1,349 (as of 11 October 2005)

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 immunizing 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 Immunization 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 US-led drive against Islam. [5] 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

1,354 cases of poliovirus

Source: Polio cases for 2005, as of week 11 October

  489 Nigeria (endemic)
  472 Yemen (importation)
  264 Indonesia (importation)
   37 India (endemic)
   26 Sudan (re-established transmission)
   18 Pakistan (endemic)
   17 Ethiopia (importation)
    8 Angola (importation)
    4 Niger (endemic)
    4 Afghanistan (endemic)
    3 Mali (importation)
    3 Somalia (importation)
    1 Chad (re-established transmission)
    1 Cameroon (importation)
    1 Eritrea (importation)
    1 Nepal (importation)

Source: Star Tribune

    5 United States

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 Feb. 27 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." [6]

Sudan

"Since the beginning of 2005, the ICRC's various primary health clinics have managed to immunize more than 99,000 children under five years of age against poliomyelitis. In all, 78,654 children were immunized 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 immunization campaign and the ICRC has provided its support, particularly in conflict-affected regions." [7]

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 recorded 4,791 cases of polio in 1994, 1,600 in 2002, 225 in 2003, and 135 in 2004. [8] "Afghanistan, India and Pakistan are on target to eradicate polio in 2005, according to international health organizations." [9]

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." [10]

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. [11] [12]

New public fears over the 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.[13]

United States

Poliovirus Infections in Four Unvaccinated Children: "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

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.

Scandals

There were two proposed vaccines introduced before Jonas Salk's vaccine in 1953. In 1935 Maurice Brody, a research assistant at New York University, claimed to have discovered a vaccine procured from ground up monkey spinal cords. He tested the vaccine on himself and several of his assistants. He gave the vaccine to three thousand children and many had developed allergic reactions, but no immunity to polio. Other researchers could not replicate his experiment.

John Kolmer also claimed to have developed a vaccine, and not only was that false, but it proved to be fatal to many children.

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 [14] 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.

External links

• Elimination of Polio in Latin America and the Caribbean
• Franklin D. Roosevelt's granddaughter expresses hope that total eradication of polio is imminent on the occasion of the 50th Anniversary of the Salk polio vaccine. Audio and story available.
• Global Polio Eradication
• Rotary International: PolioPlus
• Travel advisory issued due to polio in Nigeria
• University of Pittsburgh's Jonas Salk and Polio information
• Pittsburgh Post-Gazette feature on 50 years of Polio Vaccine and the disease's current forms
• Polio vaccination