Science Fair Project Encyclopedia
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 lining . It may proceed to the blood stream and into the central nervous system causing muscle weakness and often paralysis.
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. The Roman emperor Claudius was stricken as a child and walked with a limp for the rest of his life. United States president Franklin Delano 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.
What is polio?
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 to five. The incubation period of polio, from the time of first exposure to first symptoms, is from three to thirty five days.
Polio can spread widely before physicians detect the first signs of a polio outbreak and infections. 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, pain in the neck and extremities.
Types of 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 muscle limbs. 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 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; and the nerve that sends signals to the heart, intestines, respiratory (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, decades later; these symptoms are called post-polio syndrome.
First effective vaccine
The first effective polio vaccine was developed by Jonas Salk, although it was the vaccine developed by Albert Sabin that was used for mass inoculation. The first inoculations of children against polio began in Pittsburgh, Pennsylvania on February 23, 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. 
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 current plan calls 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 sterility in boys.
If polio is eradicated it will be the second disease to be eradicated. The first one was smallpox.
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.  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.
The World Health Organization had hoped to wipe out the disease in 2004, but the number of cases rose to 1,185 in 17 countries up from 784 in 15 countries in 2003. Asia halved its toll, but cases doubled in Africa to 1,037. Nigeria, Africa's most populous nation, accounted for 763 cases, followed by India with 129 and Sudan with 112.
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.
- Global Polio Eradication
- Travel advisory issued due to polio in Nigeria
- Rotary International: PolioPlus
- 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.
- Elimination of Polio in Latin America and the Caribbean
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