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Polio
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The Global Poliomyelitis Eradication Initiative has succeeded in reducing cases by 99%, preventing 5 million cases since creation in 1988.1
Poliomyelitis is caused by three types of Enterovirus.2 The virus is transmitted by person-to-person contact through the fecal-oral route. Infection begins in the gastrointestinal tract and spreads to lymph nodes and sometimes to the central nervous system. Infection can occur from both wild-type and vaccine-derived strains of poliovirus.
- Poliovirus remains transmissible through saliva or mucus from the throat for one week and in feces for three to six weeks.2 Polio is most problematic in communities with poor sanitation and hygiene.
- Among 100 people infected with polio, 90 will experience fevers or mild to no symptoms and 10 will develop fevers, nausea, vomiting, weakness and headaches.2
- Death may occur if muscles for breathing or swallowing are paralyzed. Poliovirus type-1 is most often linked with paralysis and epidemics.
- In 1999, type-2 polio was rarely found in paralytic cases; transmission of wild type-2 virus was interrupted in 1999 and has been nearly eliminated worldwide.3
- Type-3 polio is often linked with infections resulting from contact with someone vaccinated and is sometimes paralytic. In 2007, 1,261 cases were reported.4
- About 1% of those with polio develop meningitis or experience muscle pain that can progress to paralysis with neck and back stiffness if damage occurs to the spinal chord or brain.2
Prior to the development and distribution of the first vaccine, annual polio epidemics occurred around the world, including in the United States.2, 4 In 1955, Jonas Salk created the intramuscular poliovirus vaccine (IPV), which uses “dead” virus and is injected. Six years later, Albert Sabin developed the oral poliovirus vaccine (OPV) from a live-attenuated (weakened) form of the virus.
The Global Polio Eradication Initiative began in 1988, when 350,000 deaths were occurring annually across 125 countries.1 The goal was to eradicate polio by 2000 – targets for eradication were not met in some regions. Polio is still endemic in four countries.
| Countries |
Eradication Challenge |
Total Cases in 2007 |
Total Cases in 2009 |
| India |
Viral spread is very strong |
471 |
559 |
| Pakistan |
Major security issues, political strife, war |
24 |
117 |
| Afghanistan |
Major security issues, political strife, war |
13 |
31 |
| Nigeria |
Weak immunizations delivery system2 |
279 |
798 |
- In 2009, these four endemic countries comprised 91 percent of reported cases.5
- Between 80% and 90% of cases occur among children aged 3 years and under; most of the remaining cases occur among children under age 5 years.2
- Innovative, country-specific strategies are needed, as is political will.1
- The populations most at-risk for polio infection include groups opposed to immunizations, minorities, migrants, refugees and others living in poverty that have difficulty accessing immunization services.2
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| 1 |
World Health Organization. 2007. The case for completing polio eradication. Available from: www.polioeradication.org/content/publications/TheCase_FINAL.pdf |
| 2 |
Heymann DL, editor. Control of communicable diseases manual with addendeum to influenza data: updated April 18, 2006. 18 ed. Washington, DC: American Public Health Association, 2004. |
| 3 |
Orr D. 2007. India last bastion of polio at "tipping point". Bulletin of WHO 85(11):828-9 |
| 4 |
Global Polio Eradication Initiative. The disease and the virus. (accessed December 1, 2009), Available from: www.polioeradication.org/disease.asp |
| 5 |
UNICEF. Immunization: eradicating polio. (accessed December 1, 2009), Available from: www.unicef.org/immunization/index_polio.html |
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