POLIO

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Medical Encyclopedia: Poliomyelitis

Alternative names
Polio; Infantile paralysis

Definition

Poliomyelitis is a viral disease that can affect nerves and lead to paralysis.

Causes, incidence, and risk factors

Poliomyelitis is a disease caused by infection with the poliovirus. The virus spreads by direct person-to-person contact, by contact with infected mucus or phlegm from the nose or mouth, or by contact with infected feces.

The virus enters through the mouth and nose, multiplies in the throat and intestinal tract, and then is absorbed and spread through the blood and lymph system. The time from being infected with the virus to developing symptoms of disease (incubation) ranges from 5 - 35 days (average 7 - 14 days).

Risks include:

* Lack of immunization against polio and then exposure to polio
* Travel to an area that has experienced a polio outbreak

In areas where there is an outbreak, those most likely to get the disease include children, pregnant women, and the elderly. The disease is more common in the summer and fall.

Between 1840 and the 1950s, polio was a worldwide epidemic. Since the development of polio vaccines, the incidence of the disease has been greatly reduced. Polio has been wiped out in a number of countries. There have been very few cases of polio in the Western hemisphere since the late 1970s. Children in the United States are now routinely vaccinated against the disease.

Outbreaks still occur in the developed world, usually in groups of people who have not been vaccinated. Polio often occurs after someone travels to a region where the disease is common. Thanks to a massive global campaign over the past 20 years, polio exists only in a few countries in Africa and Asia.

Symptoms

There are three basic patterns of polio infection: subclinical infections, nonparalytic, and paralytic. Approximately 95% of infections are subclinical infections, which may not have symptoms.

SUBCLINICAL INFECTION

* General discomfort or uneasiness (malaise)
* Headache
* Red throat
* Slight fever
* Sore throat
* Vomiting

People with subclinical polio infection might not have symptoms, or their symptoms may last 72 hours or less.

Clinical poliomyelitis affects the central nervous system (brain and spinal cord), and is divided into nonparalytic and paralytic forms. It may occur after recovery from a subclinical infection.

NONPARALYTIC POLIOMYELITIS

* Back pain or backache
* Diarrhea
* Excessive tiredness, fatigue
* Headache
* Irritability
* Leg pain (calf muscles)
* Moderate fever
* Muscle stiffness
* Muscle tenderness and spasm in any area of the body
* Neck pain and stiffness
* Pain in front part of neck
* Pain or stiffness of the back, arms, legs, abdomen
* Skin rash or lesion with pain
* Vomiting

Symptoms usually last 1 - 2 weeks.

PARALYTIC POLIOMYELITIS

* Abnormal sensations (but not loss of sensation) in an area
* Bloated feeling in abdomen
* Breathing difficulty
* Constipation
* Difficulty beginning to urinate
* Drooling
* Fever 5 - 7 days before other symptoms
* Headache
* Irritability or poor temper control
* Muscle contractions or muscle spasms in the calf, neck, or back
* Muscle pain
* Muscle weakness, asymmetrical (only on one side or worse on one side)
o Location depends on where the spinal cord is affected
o Progresses to paralysis
o Rapid onset
* Sensitivity to touch; mild touch may be painful
* Stiff neck and back
* Swallowing difficulty

Signs and tests

The health care provider may find signs of meningeal irritation (similar to meningitis), such as stiff neck or back stiffness with difficulty bending the neck. The person also might have difficulty lifting the head or lifting the legs when lying flat on the back, and abnormal reflexes.

Tests include:

* Routine CSF examination
* Test for levels of antibodies to the polio virus
* Viral cultures of throat washings, stools, or cerebrospinal fluid (CSF)

Treatment

The goal of treatment is to control symptoms while the infection runs its course.

People with severe cases may need lifesaving measures, especially breathing help.

Symptoms are treated based on how severe they are. Treatments include:

* Antibiotics for urinary tract infections
* Medications (such as bethanechol) for urinary retention
* Moist heat (heating pads, warm towels) to reduce muscle pain and spasms
* Pain killers to reduce headache, muscle pain, and spasms (narcotics are not usually given because they increase the risk of breathing difficulty)
* Physical therapy, braces or corrective shoes, or orthopedic surgery to help recover muscle strength and function

Expectations (prognosis)

The outcome of the disease depends on the form (subclinical, nonparalytic, or paralytic) and the site affected. If the spinal cord and brain are not affected, which is the case more than 90% of the time, complete recovery is likely.

Brain or spinal cord involvement is a medical emergency that may result in paralysis or death (usually from respiratory difficulties).

Disability is more common than death. Infection high in the spinal cord or in the brain increases the risk of breathing problems.

Complications

* Aspiration pneumonia
* Cor pulmonale
* High blood pressure
* Kidney stones
* Lack of movement
* Lung problems
* Myocarditis
* Paralytic ileus (loss of intestinal function)
* Permanent muscle paralysis, disability, deformity
* Pulmonary edema
* Shock
* Urinary tract infections

Calling your health care provider

Call your health care provider if:

* Someone close to you has developed poliomyelitis and you haven't been vaccinated
* You develop symptoms of poliomyelitis
* Your child's polio immunization (vaccine) is not up to date

Prevention

Polio immunization (vaccine) effectively prevents poliomyelitis in most people (immunization is over 90% effective).

Update Date: 1/22/2008

Updated by: Kenneth M. Wener, MD, Department of Infectious Diseases, Lahey Clinic, Burlington, MA. Review provided by VeriMed Healthcare Network.

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Fact sheet N°114
Updated January 2008
Poliomyelitis

Key facts

* 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.

Polio and its symptoms

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. 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). Among those paralysed, 5% to 10% die when their breathing muscles become immobilized.

People most at risk

Polio mainly affects children under five years of age.

Prevention

There is no cure for polio, it can only be prevented. Polio vaccine, given multiple times, can protect a child for life.

Global caseload

Polio cases have decreased by over 99% since 1988, from an estimated 350 000 cases in more than 125 endemic countries then, to 1997 reported cases in 2006. In 2008, only parts of four countries in the world remain endemic for the disease - the smallest geographic area in history.

The Global Polio Eradication Initiative

Launch

In 1988, the forty-first World Health Assembly, consisting then of delegates from 166 Member States, adopted a resolution for the worldwide eradication of polio. It marked the launch of the Global Polio Eradication Initiative, spearheaded by the World Health Organization (WHO), Rotary International, the US Centers for Disease Control and Prevention (CDC) and UNICEF. This followed the certification of the eradication of smallpox in 1980, progress during the 1980s towards elimination of the poliovirus in the Americas, and Rotary International’s commitment to raise funds to protect all children from the disease.

Progress

Overall, in the 20 years since the Global Polio Eradication Initiative was launched, the number of cases has fallen by over 99%. In 2008, only four countries in the world remain polio-endemic.

In 1994, the World Health Organization (WHO) Region of the Americas (36 countries) was certified polio-free, followed by the WHO Western Pacific Region (37 countries and areas including China) in 2000 and the WHO European Region (51 countries) in June 2002.

In 2007, more than 400 million children were immunized in 27 countries during 164 supplementary immunization activities (SIAs). Globally, polio surveillance is at historical highs, as represented by the timely detection of cases of acute flaccid paralysis.

Persistent pockets of polio transmission in northern India, northern Nigeria and the border between Afghanistan and Pakistan are key epidemiological challenges.

Objectives

The objectives of the Global Polio Eradication Initiative are:

* To interrupt transmission of the wild poliovirus as soon as possible;
* To achieve certification of global polio eradication;
* To contribute to health systems development and strengthening routine immunization and surveillance for communicable diseases in a systematic way.

Strategies

There are four core strategies to stop transmission of the wild poliovirus in areas that are affected by the disease or considered at high risk of re-infection:

* high infant immunization coverage with four doses of oral poliovirus vaccine (OPV) in the first year of life;
* supplementary doses of OPV to all children under five years of age during SIAs;
* surveillance for wild poliovirus through reporting and laboratory testing of all acute flaccid paralysis (AFP) cases among children under fifteen years of age;
* targeted “mop-up” campaigns once wild poliovirus transmission is limited to a specific focal area.

Before a WHO region can be certified polio-free, three conditions must be satisfied: (a) there are at least three years of zero polio cases due to wild poliovirus; (b) disease surveillance efforts in countries meet international standards; and (c) each country must illustrate the capacity to detect, report and respond to “imported” polio cases. Laboratory stocks must be contained and safe management of the wild virus in inactivated polio vaccine (IPV) manufacturing sites must be assured before the world can be certified polio-free.

The Advisory Committee on Polio Eradication, the independent, technical body providing strategic guidance to the Global Polio Eradication Initiative, is overseeing a programme of research and consensus-building that will lead to the development of post-eradication polio immunization policy options, which will be considered by the World Health Assembly.

Coalition

The Global Polio Eradication Initiative (GPEI) is spearheaded by WHO, Rotary International, the US Centers for Disease Control and Prevention (CDC) and the United Nations Children’s Fund (UNICEF).

The polio eradication coalition includes governments of countries affected by polio; private sector foundations (e.g. United Nations Foundation, Bill & Melinda Gates Foundation); development banks (e.g. the World Bank); donor governments (e.g. Australia, Austria, Belgium, Canada, Denmark, Finland, France, Germany, Iceland, Ireland, Italy, Japan, Luxembourg, Malaysia, Monaco, the Netherlands, New Zealand, Norway, Oman, Portugal, Qatar, the Republic of Korea, the Russian Federation, Saudi Arabia, Spain, Sweden, Switzerland, Turkey, United Arab Emirates, the United Kingdom and the United States of America); the European Commission; humanitarian and nongovernmental organizations (e.g. the International Red Cross and Red Crescent societies) and corporate partners (e.g. Sanofi Pasteur, De Beers and Wyeth). Volunteers in developing countries also play a key role: 20 million people have participated in mass immunization campaigns.
Countries at risk

As long as a single child remains infected with polio, children in all countries are at risk of contracting the disease. The poliovirus can easily be imported into a polio-free country and can spread rapidly among unimmunised populations. Between 2003 and 2005, 25 previously polio-free countries were re-infected due to importations.

The four polio-endemic countries are Afghanistan, India, Nigeria and Pakistan.

Priorities for polio eradication

To stop transmission of the wild poliovirus and optimize the benefits of polio eradication, the global priorities are:

Closing the funding gap: Substantial external financial resources are required to support the efforts of endemic countries to eradicate polio. Economic modelling in 2007 demonstrated the financial and humanitarian benefits of polio eradication. Success in carrying out the necessary vaccination campaigns and surveillance hinges on sufficient funds being made available by the financial stakeholders.

Stopping wild poliovirus transmission in endemic countries: Polio is today more geographically restricted than ever before. The highest priority is reaching all children during SIAs in the remaining four endemic countries. To succeed, high levels of political commitment must be maintained at national, state/provincial and district levels. In 2007 an intensified effort to eradicate polio occurred in each of these four countries, with tailored eradication approaches to address the unique challenges of each of the infected areas. Efforts fully exploited new monovalent vaccines and diagnostics that are significantly more effective in detecting and stopping polio transmission.

IMPACT OF THE INITIATIVE

The Global Polio Eradication Initiative was launched in 1988. More than five million people who would otherwise have been paralysed are today walking because they have been immunized against polio since the initiative began.

By preventing a debilitating disease, the Global Polio Eradication Initiative is helping to reduce poverty, and is giving children and their families a greater chance of leading healthy and productive lives.

By establishing the capacity to access children everywhere, more than two billion children worldwide have been immunized during SIAs, demonstrating that well-planned health interventions can reach even the most remote, conflict-affected or poorest areas.

Planning for SIAs provides key demographic data – “finding” children in remote villages and households for the first time, and "mapping" their location for future health services.

In most countries, the Global Polio Eradication Initiative has expanded the capacity to tackle other infectious diseases, such as avian influenza or Ebola, by building effective disease-reporting and surveillance systems, training local epidemiologists and establishing a global laboratory network. This capacity has also been deployed in post-disaster health emergencies such as the aftermath of the 2004 tsunami in south-east Asia.

Routine immunization services have been strengthened by bolstering the cold chain, transport and communications systems for immunization. Improving these services helped to lay the groundwork for highly successful measles vaccination campaigns that have saved millions of young lives.

Vitamin A is often administered during polio SIAs. Since 1988, more than 1.2 million childhood deaths have been prevented through provision of vitamin A during polio SIAs.

On average, one in every 250 people in a country has been involved in polio immunization campaigns. More than 20 million health workers and volunteers have been trained to deliver OPV and vitamin A, fostering a culture of disease prevention.

Through the synchronization of SIAs, many countries have established a new mechanism for coordinating major cross-border health initiatives aimed at reaching all people – a model for regional and international cooperation for health.
Future benefits of polio eradication

Once polio is eradicated, the world can celebrate the delivery of a major global public good – something that will equally benefit all people, no matter where they live. Economic modelling published in 2007 established that significant financial benefits will also accrue from eradication.

© WHO 2009

www.who.int/mediacentre/factsheets/fs114/en/index.html

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Misc. Links

POLIOMYELITIS (pdf file)

History of Polio (WHO)

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Frequently Asked Questions about Cancer, Simian Virus 40 (SV40), and Polio Vaccine

SV40 is a virus found in some species of monkey. Soon after its discovery in 1960, SV40 was found in polio vaccine. More than 98 million Americans received one or more doses of polio vaccine during the period (1955–1963) when some of the vaccine was contaminated with SV40. SV40 has been found in certain types of human cancers, but it has not been determined that SV40 causes these cancers. The majority of evidence suggests there is no causal relationship between receipt of SV40-contaminated vaccine and cancer; however, some research results are conflicting and more studies are needed.

www.cdc.gov/vaccinesafety/concerns/archive/polio_and_cancer.htm