Frequently Asked Questions
“Poliomyelitis (polio) is a highly infectious disease caused by a virus. It invades the nervous system, and can cause total paralysis in a matter of hours. It can strike at any age, but affects mainly children under three (over 50% of all cases). The virus enters the body through the mouth and multiplies in the intestine. Initial symptoms are fever, fatigue, headache, vomiting, stiffness in the neck and pain in the limbs. One in 200 infections leads to irreversible paralysis (usually in the legs). Amongst those paralysed, 5%-10% die when their breathing muscles become immobilized. Although polio paralysis is the most visible sign of polio infection, fewer than 1% of polio infections ever result in paralysis. Poliovirus can spread widely before cases of paralysis are seen. As most people infected with poliovirus have no signs of illness, they are never aware they have been infected. After initial infection with poliovirus, the virus is shed intermittently in faeces (excrement) for several weeks. During that time, polio can spread rapidly through the community.”
“The polio virus enters the body through the mouth, usually from hands contaminated with the stool of an infected person.
Polio is preventable by immunization.
Since polio immunization has become widespread in the United States, cases of polio are rare. However, polio remains a problem in many parts of the world.”
“Polio, short for poliomyelitis, is a disease that can damage the nervous system and cause paralysis. Since polio immunization has become widespread in the United States, cases of polio are rare. However, polio remains a problem in many parts of the world.”
“Polio is a highly contagious disease that is caused by a virus that primarily lives in the intestines and human feces1,2 The poliovirus is spread from person-to- person primarily through oral contact with the feces of an infected person (for example, by changing diapers); it can also spread through contaminated food or water, especially in areas with poor sanitation systems.1,2 There have also been cases that have been transmitted by direct oral contact or by droplet spread3 Once inside the body, the poliovirus multiplies in the throat and intestinal tract, then travels through the bloodstream where it infects the brain and spinal cord1,2 Paralysis occurs because the poliovirus attacks the nervous system and damages or destroys the nerves that send messages between the brain and the muscles1,2”
“In the remaining polio endemic countries, poliovirus is mainly passed through person-to-person contact. Most people infected with the poliovirus do not develop polio paralysis or other symptoms of polio infection. However one in 200 people do have symptoms and can become paralyzed. The virus enters the environment through faeces of people infected then is passed to others especially in situations of poor hygiene. The poliovirus can also infect persons who have been vaccinated and can be carried by them. Such individuals will not develop polio, but can carry the virus in their intestines and can pass it to others in conditions of sub-standard hygiene. The disease may infect thousands of people, depending on the level of sanitation, before the first case of polio paralysis emerges. Individuals can carry the virus in their intestines just long enough to transmit to others. WHO considers a single confirmed case of polio paralysis to be evidence of an epidemic – particularly in countries where very few cases occur.”
“Poliovirus is spread through person-to-person, fecal-oral contact. Where hygiene and sanitation are poor, young children are especially at risk. 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.
The disease circulates “silently” at first, and may infect hundreds of people, depending on the level of sanitation, before the first case of polio paralysis emerges. Because of this silent transmission and the rapid spread of the disease, WHO considers a single confirmed case of polio paralysis to be evidence of an epidemic – particularly in countries where very few cases occur.”
Once established in the intestines, poliovirus can enter the blood stream and invade the central nervous system – spreading along nerve fibres. As it multiplies, the virus destroys nerve cells (motor neurons) which activate muscles. These nerve cells cannot be regenerated and the affected muscles no longer function. The muscles of the legs are affected more often than the arm muscles. The limb becomes floppy and lifeless – a condition known as acute flaccid paralysis (AFP). 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 motor neurons of the brain stem – reducing breathing capacity and causing difficulty in swallowing and speaking. Without respiratory support, bulbar polio can result in death.
Initial symptoms are fever, fatigue, headache, vomiting, stiffness in the neck and pain in the limbs. One in 200 infections leads to irreversible paralysis (usually in the legs). Among those paralysed, 5% to 10% die when their breathing muscles become immobilized.
The polio virus lives in the throat and intestinal tract of infected persons. The virus enters the body through the mouth, usually from hands contaminated with the stool of an infected person. Objects, such as eating utensils, can also spread the virus. Food and water are not thought to play a major role in the spread of polio.
Polio is diagnosed by a blood test or culture.
There is no treatment for polio. A polio patient must receive expert medical care, especially at the beginning of the illness
Two types of polio vaccine are available: oral polio vaccine (OPV) and inactivated polio vaccine (IPV).
OPV is made with a live but weakened virus. OPV protects vaccinated persons directly. OPV also protects other susceptible persons who are indirectly “vaccinated” as the vaccine virus spreads in the community. Because of wide use of OPV, no cases of paralytic polio caused by naturally circulating polio virus have been reported in the United States since 1979.
IPV is given by injection. It protects vaccinated persons as well as OPV, but it is not believed to be as effective as OPV in preventing the spread of polio virus among non-vaccinated persons. However, IPV is not known to cause polio disease.
As of January 1997, the recommended schedule for polio vaccination for children was two doses of IPV at 2 and 4 months of age, followed by two doses of OPV at 12-18 months and 4-6 years. This schedule is expected to reduce the small number of polio cases caused by the oral vaccine.
Schedules containing all OPV or all IPV can still be used, too. IPV can be given at 2, 4, and 12-18 months, and 4-6 years. OPV can be given at 2, 4, and 6-18 months, and 4-6 years. Parents and doctors can choose among the three schedules.
Booster doses of polio vaccine are also recommended for persons traveling to areas of the world where polio is still a problem.
As is the case with all immunizations, there are important exceptions and special circumstances. Health-care providers should have the most current information on recommendations about polio vaccination.
This fact sheet is for information only and is not meant to be used for self-diagnosis or as a substitute for consultation with a health-care provider. If you have any questions about the disease described above, consult a health-care provider.
PPS is caused by the death of individual nerve terminals in the motor units that remain after the initial attack of polio. This deterioration of individual nerve terminals might be an outcome of the recovery process from the acute polio attack. During this recovery process, in an effort to compensate for the loss of nerve cells (neurons), surviving motor neurons sprout new endings to restore function to muscles. This results in large motor units that may add stress to the body. As a result of this rejuvenation, the individual may have normal-functioning muscles for some time. But after a number of years, the motor neurons with excessive sprouting may not be able to maintain the metabolic demands of all their new sprouts, and a slow deterioration of the individual terminals may result.
Restoration of nerve function may occur in some fibers a second time, but eventually nerve terminals are destroyed and permanent weakness occurs. This hypothesis is consistent with PPS’s slow, stepwise, unpredictable course. Through years of studies, scientists at the National Institute of Neurological Disorders and Stroke have shown that PPS is a very slowly progressing condition marked by long periods of stability.
Scientists are working on a wide variety of treatment possibilities for patients with PPS, including drug treatments, some of which show promise. Doctors at the National Institutes of Health (NIH) have tried treating PPS patients with alpha 2 recombinant interferon, but the treatment proved ineffective. A study in which PPS patients received high doses of prednisone demonstrated a mild improvement in their condition, but the results were not statistically significant. This, in addition to the drug’s side effects, led researchers to recommend that prednisone not be used to treat PPS.
In an effort to reduce fatigue in PPS patients, scientists conducted a study using low doses of the drug pyridostigmine and found that it did reduce fatigue in some patients. Research using this drug continues. In a controlled study conducted by NIH scientists, the drug amantadine was not helpful in reducing fatigue. Scientists are also conducting more research on the use of selegiline, a drug that in an anecdotal report was thought to improve strength in PPS patients.
The future in PPS treatment may center around nerve growth factors. NINDS scientists have plans to begin a multicenter, controlled trial to test whether insulin-like growth factor (IGF-1) can enhance the ability of motor neurons to sprout new branches, maintain existing branches, and rejuvenate synapses (the space between nerve cells where signals pass from one cell to another). A preliminary study is in progress. Since PPS results from the degeneration of nerve sprouts, IGF-1 may target the heart of the problem, and may help to regenerate new sprouts. Other growth factors now under investigation have similar properties.
People who are polio survivors often ask if there is a way to prevent PPS. Presently, no prevention has been found. But doctors recommend that polio survivors follow standard healthy lifestyle practices: consuming a well-balanced diet, exercising in moderation, and visiting a doctor regularly.
The National Institute of Neurological Disorders and Stroke conducts and supports a wide range of research on neurological disorders, including PPS. For information on the research programs of the NINDS.
People may be left with varying degrees of weakness, paralysis, fatigue, muscle pain, breathing or orthopaedic problems. Others have limited paralysis or appear to have made a full recovery. Polio can result in permanent disability, and can kill.
“Polio mainly affects children under five years of age. However, immune and or partially immune adults and children can still be infected with poliovirus and carry the virus for long enough to take the virus from one country to another, infecting close contacts and contaminating sanitation systems. This could facilitate transmission especially in countries where sanitation systems are sub-standard” .
There is no cure for polio, it can only be prevented through immunization. Polio vaccine, given multiple times, almost always protects a child for life. Full immunization will markedly reduce an individual’s risk of developing paralytic polio. Full immunization will protect most people, however, individuals can still contract the disease due to the failure of some individuals to respond to the vaccine.
Polio (poliomyelitis) mainly affects children under five years of age.
One in 200 infections leads to irreversible paralysis (usually in the legs). Among those paralysed, 5% to 10% die when their breathing muscles become immobilized.
Polio cases have decreased by over 99% since 1988, from an estimated 350 000 cases then, to 1997 reported cases in 2006. The reduction is the result of the global effort to eradicate the disease.
In 2008, only four countries in the world remain polio-endemic, down from more than 125 in 1988. The remaining countries are Afghanistan, India, Nigeria and Pakistan.
Persistent pockets of polio transmission in northern India, northern Nigeria and the border between Afghanistan and Pakistan are the current focus of the polio eradication initiative.
As long as a single child remains infected, children in all countries are at risk of contracting polio. Between 2003 and 2005, 25 previously polio-free countries were re-infected due to imports of the virus.
In most countries, the global effort has expanded capacities to tackle other infectious diseases by building effective surveillance and immunization systems. Knowledge of the poliovirus has expanded with aggressive research carried out under the eradication effort.
Success for the effort hinges on closing a substantial funding gap to finance next steps of the global eradication initiative.
Before the availability of polio immunization, polio was common worldwide. However, with strong immunization programs and efforts to rid the world of polio, circulation of polio viruses is limited to a decreasing number of countries. The greatest risk is now in the Indian subcontinent and, to a lesser extent, in West and Central Africa.
Symptoms usually start 7 to 14 days after exposure to the virus. Infected persons are most contagious from a few days before to a few days after the start of symptoms. However, persons with polio can spread the infection for as long as the virus is in their throat or stool. The virus can be found in the throat for about 1 week after infection and in the stool for 6 weeks or longer.
Complications include paralysis, most commonly of the legs. Paralysis of the muscles that control breathing and swallowing can be fatal.
In very rare cases, the oral vaccine used to prevent polio can cause polio paralysis in persons who are vaccinated (1 in every 8.1 million doses) and in people who are close contacts of a vaccinated person (1 in every 5 million doses). About 8 to 9 cases of paralytic polio caused by the oral vaccine have been reported in the United States yearly.
In the United States, the last case of “wild” polio was in 1979. Wild polio is naturally circulating polio that is not caused by the oral polio vaccine. Except for an occasional importation, all cases of paralytic polio since 1979 have been caused by the oral polio vaccine. However, thousands of polo infections still occur in other parts of the world. Most cases are reported from Asia and Africa.
Post-polio syndrome (PPS) is a condition that can strike polio survivors anywhere from 10 to 40 years after recovery from an initial attack of the poliomyelitis virus. PPS is characterized by a further weakening of muscles that were previously injured by polio infection. Symptoms include fatigue, slowly progressive muscle weakness, muscle and joint pain, and muscular atrophy. Some patients experience only minor symptoms, while others develop spinal muscular atrophy or what appears to be, but is not, a form of amyotrophic lateral sclerosis (ALS), also called Lou Gehrig’s disease. PPS is rarely life-threatening.
The extent to which polio survivors will suffer from PPS depends on how seriously they were affected by the first polio attack. Patients who had only minimal symptoms from the original attack and subsequently develop PPS will most likely experience only mild PPS symptoms. People originally hit hard by the polio virus may develop a more severe case of PPS with a greater loss of muscle function, difficulty in swallowing, and more periods of fatigue.
More than 300,000 polio survivors in the United States may be at risk for PPS. Doctors are unable to establish a firm incidence rate, but they estimate that the condition affects 25 percent of these survivors.
Doctors arrive at a diagnosis of PPS after observing the patient and asking about symptoms. PPS may be difficult to diagnose in some because it is hard to determine what component of a neuromuscular deficit is old and what is new. Health professionals say that the only way to be sure a person has PPS is through a neurological examination aided by other laboratory studies that exclude all other possible diagnoses. Patients must visit the doctor periodically to establish that their muscle weakness is progressive.
Objective assessment of muscle strength in PPS patients may not be easy. A change in muscle strength is determined in specific muscle groups, or limbs, using various muscle scales, such as the Medical Research Council (MRC) scale or scales that quantify muscle force. Doctors use magnetic resonance imaging (MRI), neuroimaging, and electrophysiological studies, muscle biopsies, or spinal fluid analysis as tools to investigate the course of decline in muscle strength.
Once PPS is diagnosed, some patients worry that they have polio again, or even ALS. In general, PPS is not life-threatening. The only exception is in patients who experience severe respiratory impairment. Studies have proven that, compared to control populations, PPS patients lack any elevation of antibodies against the polio virus, and since PPS affects only certain muscle groups, it is not considered a recurrence of the original polio. Further, there is no evidence that the polio virus can cause a persistent infection in humans. Other studies have demonstrated that ALS, which progressively weakens muscles, does not occur more frequently in PPS patients, and PPS is not a form of ALS.
There has been much debate about whether to encourage or discourage exercise for polio survivors or individuals who already have PPS. Some doctors believe that too much exercise can worsen the patient’s condition, and that rest will preserve energy. These doctors think patients will wear out their muscles by overusing them in exercise activities. However, others consider this notion unfounded and not scientifically documented.
There is much misinformation on this subject and many doctors do not know what effect exercise has on individuals with PPS. A commonsense approach, in which patients use individual tolerance as their limit, is currently recommended. Tolerance is the level at which one starts having discomfort or fatigue. Researchers at the NIH are addressing the exercise issue, not only to determine if exercise is helpful, harmful, or ineffective, but also to define the most effective type — isotonic, isometric, isokinetic, or repetitive.
Scientists are working on a variety of investigations that may someday help individuals with PPS. Some basic researchers are studying the behavior of motor neurons many years after a polio attack. Others are looking at the mechanism of fatigue, and trying to tease out information from the brain, muscles, and neuromuscular junction (the site where a nerve cell meets the muscle cell it helps activate). Trying to determine if there is an immunological link in PPS is also an area of intense interest. Researchers who discovered inflammation around motor neurons in the muscle are trying to find out if this is due to an immunological response.
Other investigators are searching for the polio virus, or mutated versions of it, fragments of which have been amplified from the spinal fluid. The significance of this finding is not known however, and more research is being done.
Polio can lead to muscle paralysis that results in deformities of the hips, ankles, and feet. Although many of the deformities can be corrected with surgery and physical therapy, these treatments often aren’t available options in the developing countries where polio still exists.
Other complications associated with the prolonged hospital stay as a result of the paralysis caused by polio infection involve the lungs, kidneys, and heart:
Pulmonary edema—A potentially life-threatening condition that fills the lungs with fluid and prevents them from absorbing oxygen1.
Yes they do. Since the program was introduced into the UK in the early 1960s notifications of polio have dropped from over 6,000 in 1955 to nil today.
The risk of polio infection has been eliminated in most, but not all countries.
However, the poliovirus could be imported into a polio-free country with the risk of it spreading rapidly amongst non-immunised people.
Since October 2004, people in the UK have been vaccinated using an inactivated polio vaccine (IPV) given by injection into a muscle. This replaced the routine use of oral polio vaccine in the UK.
The IPV vaccine uses inactive (not live) poliovirus and does not cause polio. Polio vaccine, given multiple times as per advice, almost always protects for life.
Everyone should ensure that they are protected against polio before travel to countries considered a risk for polio. You are advised to seek specialist travel health advice on this – your GP or practice nurse may be helpful. If you have had polio, but have not been vaccinated, you may not have immunity against all of the polioviruses and may need polio vaccination, especially if you are travelling to “at risk” countries. Do seek advice from your health care practitioner.
Did you know?
Polio cases have decreased by over 99% since 1988, from an estimated more than 350,000 cases globally to 1,912 reported cases as of 16 January 2007. This reduction is the result of the global effort to eradicate the disease. It is estimated that there are120,000 people living in the UK who have had polio.
- Centers for Disease Control and Prevention (CDC). Epidemiology and Prevention of Vaccine-Preventable Diseases: The Pink Book. 9th ed. Washington, DC: Public Health Foundation; 2006:97-110. 2. CDC. National Immunization Program. What would happen if we stopped vaccinations? Available at: http://www.cdc.gov/nip/publications/fs/gen/WhatIfStop.htm. Accessed March 8, 2005. World Health Organization (WHO). Polio eradication: now more than ever, stop polio forever. Available at: http://www.who.int/features/2004/polio/en. Accessed March 22,2005.
- Centers for Disease Control and Prevention (CDC). Epidemiology and Prevention of Vaccine-Preventable Diseases: The Pink Book. 9th ed. Washington, DC: Public Health Foundation; 2006:97-110. 2. MayoClinic.com. Polio. Available at: http://www.mayoclinic.com/invoke.cfm?id=DS00572 Accessed March 21, 2005. 3. Plotkin SA, Orenstein WA, eds. Vaccines. 4th edition: WB Saunders. Philadelphia, Pa: 2004;658.
- Centers for Disease Control and Prevention (CDC). Epidemiology and Prevention of Vaccine-Preventable Diseases: The Pink Book. 9th ed. Washington, DC: Public Health Foundation; 2006:97-110. 2. MayoClinic.com. Polio. Available at: http://www.mayoclinic.com/invoke.cfm?id=DS00572. Accessed March 21, 2005.
- http://www.mayoclinic.com/invoke.cfm?id=DS00572. Accessed March 21, 2005.
- Centers for Disease Control and Prevention (CDC). Epidemiology and Prevention of Vaccine-Preventable Diseases: The Pink Book. 9th ed. Washington, DC: Public Health Foundation; 2006:97-110. 2. MayoClinic.com. Polio. Available at: http://www.mayoclinic.com/invoke.cmf?objectid=DS00572. Accessed March 21, 2005.
- Centers for Disease Control and Prevention (CDC). Epidemiology and Prevention of Vaccine-Preventable Diseases: The Pink Book. 9th ed. Washington, DC: Public Health Foundation; 2006:97-110. 2. CDC. Recommended childhood and adolescent immunization schedule-United States, 2005. MMWR. 2005;53:Q1-Q3. 3. IPOL® (Poliovirus Vaccine Inactivated) Prescribing Information, December 2005.
- Very Important Source: http://www.polio.com/?fa=learn/polio/vaccines/history