Questions and Answers on Polio
Q What is poliomyelitis?
Poliomyelitis (polio) is a highly infectious disease caused by a virus that invades the nervous system and can cause total paralysis in a matter of hours. Approximately one in 200 infections leads to irreversible paralysis, usually in the legs. Among those paralysed, five to ten per cent die when their breathing muscles become immobilized. Poliomyelitis mainly affects children under 5 years of age.
Q How is it transmitted?
The virus enters the body through the mouth and multiplies in the intestine. It invades the nervous system and can cause total paralysis in a matter of hours.
Q How can poliomyelitis be treated?
Global Polio Eradication Initiative
Q What is eradication?
Eradication of poliomyelitis is defined as ending the transmission of the wild poliovirus, meaning that no children will be paralysed by the wild poliovirus.
Q Why eradicate poliomyelitis?
Poliomyelitis is one of the few diseases that can be eradicated because it cannot survive long outside the human body, and an inexpensive and effective immunization mechanism, oral polio vaccine (OPV), is available.
The humanitarian impact of eradicating poliomyelitis is enormous - by 2005 five million children in the developing world who would have been paralysed will be walking because they have been immunized against poliomyelitis. Polio eradication is a global public good - something from which all people can benefit for all time.
Q Have any other diseases been eradicated?
Q What is the Global Polio Eradication Initiative?
Q Who is involved in the Global Polio Eradication Initiative?
The Initiative 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: the governments of countries affected by poliomyelitis; private foundations such as the United Nations Foundation and Bill & Melinda Gates Foundation; development banks such as the World Bank; donor governments such as Australia, Austria, Belgium, Canada, Denmark, Finland, Germany, Ireland, Italy, Japan, Luxembourg, Netherlands, Norway, United Kingdom and United States of America; the European Commission; non-governmental organizations; humanitarian organizations such as the International Red Cross and Red Crescent societies; and corporate partners such as Aventis Pasteur and De Beers.
Volunteers and health workers in developing countries also play a key role: 10 million have participated in mass immunization campaigns.
Q What are the strategies for eradicating polio?
The four key strategies for eradicating poliomyelitis are:
1) routine immunization of infants with OPV in the first year of life;
2) supplementary immunisation activities, national immunization days and sub-national immunisation days (NIDs and SNIDs), during which all children under five years of age are vaccinated, regardless of whether they have been vaccinated before;
3) mop-up campaigns, to ensure that every child is vaccinated and to break the final chains of transmission; and
4) effective disease surveillance for acute flaccid paralysis (AFP) to find and investigate every newly paralysed child to determine if poliomyelitis is the cause of the paralysis.
Q Which vaccine is recommended for polio eradication?
Oral polio vaccine is safe, effective, inexpensive, and the recommended vaccine for the global effort to eradicate poliomyelitis. Because of its high levels of immunity, especially in the intestines, it is the only vaccine proven to stop transmission of the virus in developing countries. OPV is easy to deliver. It drops from a vial into the mouth of the child and can be administered by volunteers as well as trained health workers.
Status of the Global Polio Eradication Initiative
Q What has been achieved globally?
The Global Polio Eradication Initiative has made tremendous progress toward its goal. Two of the six WHO regions have been certified as polio-free (the Americas and the Western Pacific regions) and the European Region could be certified on 21 June 2002.
In the remaining WHO regions significant progress continues to be made. As of 10 June 2002 480 cases were reported globally in 2001, representing a 99.8% decline in the number of cases since the initiative began in 1988, when 350 000 cases were estimated to occur each year. In the same time period, the number of polio-endemic countries dropped from 125 to just 10.
Q Which countries still have poliomyelitis?
The remaining polio-endemic countries are Afghanistan, Angola, Egypt,
Ethiopia, India, Niger, Nigeria, Pakistan, Somalia, and Sudan. Five
of the ten countries accounted for 96% of all new cases in 2001 and
are considered the high-transmission areas. They are Northern India,
Pakistan/Afghanistan and Nigeria/Niger.
Q When will the transmission of wild poliovirus be stopped?
Countries in the low transmission areas can stop transmission by mid-2002 provided all children under five are reached during the NIDs and there is no deterioration of security. The countries in high transmission zones - India, Pakistan, Afghanistan, Nigeria and Niger - are aiming to stop transmission by the end of the year. A review of progress in these countries will be undertaken late in the year to determine whether there is some risk of continuing transmission into 2003.
Q Which areas pose the greatest risk to the goal of interrupting transmission by the end of 2002?
The global Technical Consultative Group on poliomyelitis eradication
(TCG) determined that India, Pakistan and Nigeria pose the greatest
risk to the target date, due to continued high-intensity transmission,
high population density, and low routine immunization coverage. However,
these three countries have made tremendous progress towards eradication
and are recording cases in smaller and smaller areas, indicating that
transmission is increasingly confined to certain geographical areas,
despite certification-standard surveillance.
Afghanistan continued to make progress towards poliomyelitis eradication, despite the events of 11 September. The country conducted two rounds of NIDs in September and November and reached most of the children targeted. Another NID was conducted in April 2002 and was carefully coordinated with Pakistan to ensure good coverage in the border areas. The impact on the eradication programme included disruption of some activities on the ground and a deterioration of the surveillance system. A priority for the program is to re-establish certification-standard surveillance as soon as possible. The long-term impact could include a lull in financing, as donors' priorities shift.
Q What does certification mean?
Q Will the world be ready for global polio-free certification in 2005?
Status of the WHO European Region
Q What was the status of transmission of poliovirus when the eradication initiative began in the European Region?
The thirty-ninth session of the Regional Committee endorsed the target of regional poliomyelitis elimination by 2000 in September 1990. By 1990 significant progress had already been made in controlling poliomyelitis throughout much of Europe and it appeared that 32 countries had interrupted transmission. However, transmission of wild poliovirus remained intense in the central Asian republics, Caucasus republics and Turkey with 354 cases reported from 14 countries.
Q How was transmission of wild poliovirus stopped in the European Region?
There were numerous challenges to achieving the goal of interrupting
transmission of wild poliovirus in such a large, geographically and
demographically diverse region. The social and economic changes following
the dissolution of the USSR and redefinition of national borders in
south central Europe impacted the programme with delivery of immunization
services and vaccine supply being disrupted in many parts of the region.
Large outbreaks occurred in the early 1990s. The epidemiological situation indicated that interrupting transmission in a large geographical area would require high immunization coverage and effective cross border surveillance. Operation MECACAR was introduced with this purpose in 1995, organizing synchronized NIDs across 18 countries in the European and Eastern Mediterranean Regions, and successfully interrupted transmission of wild poliovirus in large geographic areas.
Surveillance provided valuable information guiding end-stage mop-up
campaigns in areas where transmission persisted. This surveillance data
identified a reservoir of poliovirus transmission in Turkey, from which
26 cases were detected in 1998, shared with northern Iraq. Intensive
mop-up immunization activities were conducted, apparently stopping transmission
of wild poliovirus as the last reported cases of poliomyelitis in the
Region due to indigenous wild poliovirus has onset of paralysis on 26
Operation MECACAR is an unprecedented coordinated polio eradication effort across 18 countries and areas in the Mediterranean, Caucasus and Central Asia. This initiative synchronized NIDs in 10 MECACAR countries European Region (Armenia, Azerbaijan, Georgia, Kazakhstan, Kyrgystan, Russian Federation, Tajikistan, Turkey, Turkmenistan and Uzbekistan) as well as with 8 neighbouring countries in the Eastern Mediterranean Region. Operation MECACAR achieved 92% coverage reaching up to 60 million children for vaccination and appeared to have interrupted transmission of wild poliovirus in large geographic areas.
After the success of the initiative, 'Operation MECACAR Plus', continued collaboration of the MECACAR countries was started in 1998.
Q What is the status of polio-free certification of the European
The last identified indigenous poliovirus case in Europe was in Melik Minas, who was 33 months old when he was paralysed by poliomyelitis in South Eastern Turkey on 26 November 1998. He had never been vaccinated against poliomyelitis. In November 2001, the WHO European Region marked three years of being free of confirmed indigenous poliomyelitis cases.
As no indigenous wild poliovirus has been isolated under conditions
of certification-standard surveillance in any member state of the WHO
European Region since November 1998, the region is on track for certification
when the WHO European Regional Commission for Certification of Poliomyelitis
Eradication meets on 21 June 2002.
The European Regional Certification Commission is an independent panel of eight experts in public health, epidemiology, virology, and clinical medicine. The Commission was established in March 1996.
Q How will the Commission determine whether to certify the European Region polio-free?
The Certification Commission has the responsibility to review data and background for all Member States to determine whether or not there is sufficient evidence that transmission of wild poliovirus has been interrupted. The Commission has been reviewing country specific documentation since 1999. Specific issues being addressed by the Commission include:
Q What are the current challenges to certification for the European Region?
When the Regional Certification Commission met in March 2002, more than three years after the last reported case of indigenous poliomyelitis in the region, its members identified areas requiring additional documentation or action. These include the provision of additional documentation on the interruption of transmission of a wild poliovirus importation into Georgia and Bulgaria from south Asia in mid-2001, national plans for continuing immunization and surveillance activities through global certification, and survey and inventory of facilities holding wild poliovirus stocks or potentially infectious materials according to agreed timelines. The RCC will be reviewing the status of each of these areas at its meeting in June.
Q What is an importation?
Importation occurs when a poliovirus is introduced into an area in which it did not previously circulate. An importation can result in virus transmission being re-established in an area that is considered polio-free, if the importation is not detected and responded to quickly.
All countries remain at risk of importations until transmission of wild poliovirus is interrupted globally, demonstrating the fragility of any area's polio-free status. High immunization coverage is required to prevent an imported virus from finding an under-immunized, susceptible population in which transmission can continue. A sensitive surveillance system, able to quickly detect and identify any importation and guide a programmatic response, is critical. The WHO European Region detected two importations, to Bulgaria and Georgia, in 2001 alone.
Q How do imported cases of poliomyelitis affect the certification process?
The global TCG has determined that when an importation is identified, targeted immunization must take place immediately to prevent further infection, followed by careful surveillance. Importation of poliovirus does not affect certification status as long as it is dealt with promptly and appropriately and does not re-establish prolonged or extensive circulation of the virus.
Q How does the outbreak in Bulgaria affect certification of the European Region?
The outbreak in Bulgaria early in 2001 was caused by a Type-1 wild poliovirus imported from the Indian sub-continent. The outbreak caused 3 cases of paralysis from March to May, and affected children in the Roma community - a traditionally under-immunized population. The government of Bulgaria responded very quickly to stop the outbreak, by conducting sub-NIDs in April followed by NIDs in May and June. Surveillance has been enhanced to ensure there are no additional cases.
The WHO European Regional Office approached all countries of central and southern Europe with high-risk subpopulations, such as refugees and immigrants. Countries were encouraged to review the vaccination status of high-risk populations, strengthen surveillance and take additional action as necessary. The size of response actions taken by countries varied in scale.
As the outbreak was contained within months of the index case, the Commission has stated that the regional certification timeline will not be affected. The WHO European Region remains on track for certification in June 2002.
Q What happened in Georgia and what has been the response?
In December 2001, a wild poliovirus was isolated from a 5-year-old boy who had symptoms of meningitis/encephalitis with onset from September. Type-1 wild poliovirus was isolated, closely resembling viruses currently circulating in the Indian sub-continent. The child was diagnosed with non-paralytic polio.
Following local immunization of children and enhanced surveillance, two rounds of NIDs were conducted in March/April and April/May 2002. Armenia and Azerbaijan conducted mass immunization campaigns in the appropriate bordering territories. The Commission will be reviewing additional documentation on the interruption of transmission of the imported wild poliovirus in Georgia prior to making its decision on European certification in June.
Q What poliomyelitis eradication activities will be continued in the European Region after certification and why?
The Regional Certification Commission will continue to meet yearly for updates on polio eradication activities in the Region. All countries will need to maintain high immunization coverage, paying special attention to vulnerable subpopulations, and to sustain high quality laboratory based surveillance through global certification. Recent experiences with importations into the region have highlighted this need.
Countries will need to implement activities to survey laboratories
that may have stocks of wild poliovirus and ensure laboratory containment
of wild polioviruses, preparing for global eradication by limiting reservoirs
An immediate response with supplemental immunization would be required, similar to the prompt action taken in response to the importations into Bulgaria and Georgia, discussed earlier. The objective of the immunization activities would be to ensure that imported virus is not allowed to establish transmission locally.
A report would be required by the Regional Certification Commission detailing the action taken and evidence that the importation was controlled - meaning that there was no transmission more than six months after the importation, followed by a final report one year after the importation.
The Commission has asked each country to provide a plan of action for this circumstance in advance of the certification meeting.
Looking forward - Global Programme
Q What are the major challenges to poliomyelitis eradication?
The remaining global priorities for poliomyelitis eradication are
Q What is the funding gap and what is being done to overcome it?
Q What is being done to reach all children, particularly those affected
Q As more countries are free of it, what happens to the wild poliovirus?
As an increasing number of countries become polio-free, the virus is safely and securely stored in a limited number of laboratories to ensure no inadvertent release occurs after eradication. A unanimous resolution at the World Health Assembly in May 1999 called for all laboratories to either transfer virus to designated WHO repositories, implement high containment procedures or destroy stocks of the virus if they are not useful to research.
Q Why can't countries stop vaccination after certification?
The decision as to when and how any country stops vaccination must be viewed in a global perspective. Until global certification of poliomyelitis eradication, all areas remain at risk of importation of poliovirus and must ensure high population immunity to maintain polio-free status.
There are a number of benefits and challenges to stopping polio vaccination. Extensive research is required before a decision regarding post-certification immunization policy can be made.
The global TCG has reaffirmed the appropriateness of the goal of stopping
immunization and has intensified its work on the evolving issue of post-certification
Q Does poliovirus present a significant threat as a biological agent?
Poliovirus presents a low level risk as a potential biologic agent relative to agents such as smallpox and anthrax. Intentional use of poliovirus as a biological agent would be inefficient, as less than 1% of those infected become paralysed and less than 0.1% die. The potential for poliomyelitis to be disseminated to large populations is low, as poliovirus is sensitive to drying and does not survive in the environment. High immunization coverage at this point in time further reduces the potential to spread the virus. Public health preparedness to detect and control poliomyelitis is currently high.
Q What is the risk of an outbreak of circulating vaccine-derived poliovirus (cVDPV)?
Polio outbreaks due to circulating vaccine-derived polioviruses (cVDPV) are rare, but possible. An estimated 10 billion doses of OPV were administered world-wide between 1997 and 2001, a period during which there has been very high quality surveillance globally, yet only two cVDPV outbreaks have been confirmed in that period. The outbreaks, in Hispaniola and the Philippines, appear to have been stopped by supplemental immunization activities with OPV.
One previous occurrence has been documented in Egypt between 1988 and 1993. Common to all three outbreaks were a high number of previously unvaccinated people, which may have provided the conditions for VDPVs to circulate and cause disease.
Q What are the implications of cVDPV for the global initiative?
These outbreaks demonstrate the need to maintain high routine immunization coverage in all areas, to ensure high quality surveillance, and to accelerate the programme of work to determine the most appropriate immunization policy for the post-certification era, particularly if, when and how to stop use of OPV.
Q What is the 'endgame' of poliomyelitis eradication?
"Polio endgame" is the current working title for the phase of the Global Polio Eradication Initiative that aims to minimize the risks of a re-emergence or re-introduction of poliovirus and optimize the benefits of polio eradication in the post-certification era (i.e., after certification that transmission of the wild poliovirus has been interrupted). The polio endgame is a three-part programme of work which involves the containment of wild poliovirus stocks, certification of the interruption of wild poliovirus transmission and the development of post-certification immunization policy for polio. As we get closer to interrupting transmission of poliovirus, these endgame issues become increasingly important