A public health effort to eliminate all cases of poliomyelitis (polio) infection around the world, begun in 1988 and led by the World Health Organization (WHO), UNICEF and the Rotary Foundation, has reduced the number of annual diagnosed cases from the hundreds of thousands to 291 in 2012—a 99.9% reduction, though recently there has been a bounce back in some countries towards more cases. Of the three types of polio, the last recorded wild case of type 2 was in 1999. The last recorded case of type 3 was on 11 November 2012. All reported cases since 11 November 2012 have been of type 1. If polio is the next disease to be successfully eradicated, this will represent only the third time this has ever been achieved, after smallpox and rinderpest. The goal of eradicating polio worldwide has attracted international and media attention, but since 2001 progress has been erratic in reducing the number of cases, which has led to getting rid of the last 1% being described as "like trying to squeeze Jell-O to death". However, in 2011 incidence rates of the disease were dramatically reduced, and with large reduction again in 2012, hopes for eliminating polio have been rekindled. India is the latest country to successfully stop transmission of polio. May 2014, WHO declared a global health emergency for only the second time since regulations permitting it to do so were adopted in 2007, due to a spread of polio. Per the WHO, Pakistan, Syria and Cameroon have recently allowed the virus to spread — to Afghanistan, Iraq and Equatorial Guinea, respectively.
Factors influencing eradication of polio
Eradication of polio has been defined in various ways—as elimination of the occurrence of poliomyelitis even in the absence of human intervention, as extinction of poliovirus, such that the infectious agent no longer exists in nature or in the laboratory, as control of an infection to the point at which transmission of the disease ceased within a specified area, and as reduction of the worldwide incidence of poliomyelitis to zero as a result of deliberate efforts, and requiring no further control measures.
In theory, if the right tools were available, it would be possible to eradicate all infectious diseases that reside only in a human host. In reality there are distinct biological features of the organisms and technical factors of dealing with them that make their potential eradicability more or less likely. Three indicators, however, are considered of primary importance in determining the likelihood of successful eradication: that effective interventional tools are available to interrupt transmission of the agent, such as a vaccine; that diagnostic tools, with sufficient sensitivity and specificity, be available to detect infections that can lead to transmission of the disease; and that humans are required for the life-cycle of the agent, which has no other vertebrate reservoir and cannot amplify in the environment.
The most important step in eradication of polio is interruption of endemic transmission of poliovirus. Stopping polio transmission has been pursued through a combination of routine immunization, supplementary immunization campaigns and surveillance of possible outbreaks. The four key strategies outlined by the World Health Organization for stopping polio transmission are:
- High infant immunization coverage with four doses of oral polio vaccine (OPV) in the first year of life in developing and endemic countries, and routine immunization with OPV and/or IPV elsewhere.
- Organization of "national immunization days" to provide supplementary doses of oral polio vaccine to all children less than five years of age.
- Active surveillance for wild poliovirus through reporting and laboratory testing of all cases of acute flaccid paralysis. Acute Flaccid Paralysis (AFP) is a clinical manifestation of poliomyelitis characterized by weakness or paralysis and reduced muscle tone without other obvious cause (e.g., trauma). AFP is also associated with a number of other pathogenic agents including enteroviruses, echoviruses, and adenoviruses, among others. among children less than fifteen years of age.
- Targeted "mop-up" campaigns once wild poliovirus transmission is limited to a specific focal area.
Oral polio vaccine is highly effective and inexpensive (about US$0.10 per dose, or US$0.30 per child) and its availability has bolstered efforts to eradicate polio. A study carried out in an isolated Eskimo village showed that antibodies produced from subclinical wild virus infection persisted for at least 40 years. Because the immune response to oral polio vaccine is very similar to natural polio infection, it is expected that oral polio vaccination provides similar lifelong immunity to the virus.
Polio vaccination is also important in the development of herd immunity. For polio to occur in a population, there needs to be an infecting organism (poliovirus), a susceptible human population, and a cycle of transmission. Poliovirus is transmitted only through person-to-person contact and the transmission cycle of polio is from one infected person to another person susceptible to the disease, and so on. If the vast majority of the population is immune to a particular agent, the ability of that pathogen to infect another host is reduced; the cycle of transmission is interrupted, and the pathogen cannot reproduce and dies out. This concept, called community immunity or herd immunity, is important to disease eradication, because it means that it is not necessary to inoculate 100% of the population—a goal that is often logistically very difficult—to achieve the desired result. If the number of susceptible individuals can be reduced to a sufficiently small number through vaccination, then the pathogen will eventually die off.
When many hosts are vaccinated, especially simultaneously, the transmission of wild virus is blocked, and the virus is unable to find another susceptible individual to infect. Because poliovirus can only survive for a short time in the environment (a few weeks at room temperature, and a few months at 0–8 °C (32–46 °F)) without a human host the virus dies out.
Herd immunity is an important supplement to vaccination. Among those individuals who receive oral polio vaccine, only 95 percent will develop immunity. That means five of every 100 given the vaccine will not develop any immunity and will be susceptible to developing polio. According to the concepts of herd immunity this population whom the vaccine fails, are still protected by the immunity of those around them. Herd immunity can only be achieved when vaccination levels are high. It is estimated that 80–86 percent of individuals in a population must be immune to polio for the susceptible individuals to be protected by herd immunity. If routine immunization were stopped, the number of unvaccinated, susceptible individuals would soon exceed the capability of herd immunity to protect them.
Among the greatest obstacles to global polio eradication are the lack of basic health infrastructure, which limits vaccine distribution and delivery, the crippling effects of civil war and internal strife, and the sometimes oppositional stance that marginalized communities take against what is perceived as a vertical (top down) intervention. Another challenge has been maintaining the potency of live (attenuated) vaccines in extremely hot or remote areas. The oral polio vaccine must be kept at 2 to 8 °C (36 to 46 °F) for vaccination to be successful.
An independent evaluation of obstacles to polio eradication requested by the WHO and conducted in 2009 considered the major obstacles in detail by country. In Afghanistan and Pakistan, they concluded that the most significant barrier was insecurity; but that managing human resources, political pressures, the movement of large populations between and within both countries, inadequately resourced health facilities, also posed problems, as well as technical issues with the vaccine. In India, the major challenge appeared to be the high efficiency of transmission within the populations of Bihar district and Uttar Pradesh, set against the low (~80% after three doses against type 1) seroconversion response seen from the vaccine. In Nigeria, meanwhile, the most critical barriers identified were management issues, in particular the highly variable importance ascribed to polio by different authorities at the local government level, although funding issues, community perceptions of vaccine safety, inadequate mobilisation of community groups, and issues with the cold chain also played a role. Finally, in those countries where international spread from endemic countries had resulted in transmission becoming re-established—namely Angola, Chad, and South Sudan, the key issues identified were underdeveloped health systems and low routine vaccine coverage, although low resources committed to Angola and South Sudan for the purpose of curtailing the spread of polio and climatic factors were also identified as playing a role.
Two additional challenges are found in unobserved polio transmission and in vaccine-derived poliovirus. In 99% of infections, polio is a mild condition that causes very few symptoms[not in citation given] and most infected people are unaware that they carry the disease, allowing polio to spread widely before cases are seen. And since 2000, there have been a number of outbreaks of circulating vaccine-derived poliovirus, following mutations or recombinations in the attenuated strain used for the oral polio vaccine, which have raised the necessity of eventually switching to the more expensive inactivated polio vaccine.
In a 2012 interview with Pakistani newspaper Dawn, Dr. Hussain A. Gezari, WHO's special envoy on global polio eradication and primary healthcare, gave his views on obstacles to eradication. He said the biggest hurdle in making Pakistan polio-free was holding district health officials properly accountable—in national eradication campaigns officials had hired their own relatives, even young children. "How do you expect a seven-year-old thumb-sucking kid to implement a polio campaign of the government," said Dr Gezari. He added that, in spite of this, "the first national campaign was initiated by your government in 1994 and that year Pakistan reported 25,000 polio cases, and the number was just 198 last year, which clearly shows that the programme is working."
Opposition and aid worker killings
One factor contributing to the continued circulation of polio immunization programs has been opposition in some countries. This opposition has varied and is linked mostly to local political will rather than any religious orthodoxy. In Pakistan and Afghanistan, the Taliban have issued fatwas against polio vaccination.
After the September 11 attacks, a myth arose in Pakistan that the United States was using immunization campaigns to sterilize the local population. Health officials tried to dispel this story, but their efforts, in the opinion of Heidi Larson, writing in The Guardian, were marred by the Central Intelligence Agency (CIA), when it conducted a fake Hepatitis B immunization campaign in Bin Laden's residence in Bilal Town at Abbottabad with the help of Dr. Shakil Afridi. The intention of the campaign was to confirm Osama bin Laden's presence in the city by obtaining DNA samples from children suspected of being his. In a letter written to CIA director Leon Panetta, the InterAction Alliance, a union of about 200 U.S.-based non-government organizations, deplored the actions of the CIA in using a vaccination campaign as a cover. Pakistan reported the world's highest number of polio cases (198) in 2011. In early 2012, some parents refused to get their children vaccinated in Khyber Pakhtunkhwa and in the Federally Administered Tribal Areas (FATA) but religious refusals in the rest of the country had "decreased manifold".
Even with the express support of political leaders, polio workers have been kidnapped, beaten, and assassinated. In February 2007, physician Abdul Ghani, who was in charge of polio immunizations in a key area of disease occurrence in northern Pakistan, was killed in a terrorist bombing. In 2012, there was the killing of a polio worker in Gadap in October. In December 2012, a 3-day vaccination campaign sponsored by the United Nations agencies the World Health Organization and UNICEF in Pakistan was suspended following the murder of 9 vaccination workers.
The killing of polio workers seen the previous year continued in 2013. Seven clinic workers whose duties included vaccination were killed in Swabi, Pakistan on New Year's Day. The Pakistani government began providing police and paramilitary protection to a renewed vaccination campaign, but amid worries that this would inspire hostility, some escorts have been refused. Both escorting officers and polio workers continue to be killed in Pakistan, where vaccination has been said to violate Islamic law. In February a pair of similar attacks in Nigeria killed nine female polio vaccinators following a local cleric's condemnation of vaccination. The security situation in Afghanistan improved in May when the Afghani Taliban announced it would support polio eradication, pledging to do nothing to hinder the campaign as long as no foreigners were involved in the vaccinations. In December 2013, three polio workers were killed in northwest Pakistan and three more were killed in Karachi in January 2014.
includes wild-virus and vaccine-derived cases
(Current year gives cases to date for most recent update of source)
Following the widespread use of poliovirus vaccine in the mid-1950s, the incidence of poliomyelitis declined rapidly in many industrialized countries. Czechoslovakia became the first country in the world to scientifically demonstrate nationwide eradication of poliomyelitis in 1960. In 1962—just one year after Sabin's oral polio vaccine (OPV) was licensed in most industrialized countries—Cuba began using the oral vaccine in a series of nationwide polio campaigns. The early success of these mass vaccination campaigns suggested that polioviruses could be globally eradicated. The Pan American Health Organization (PAHO), under the leadership of Ciro de Quadros, launched an initiative to eradicate polio from the Americas in 1985.
In 1988, the World Health Organization, together with Rotary International, UNICEF, and the U.S. Centers for Disease Control and Prevention passed the Global Polio Eradication Initiative, with the goal of eradicating polio by the year 2000. The Initiative was inspired by Rotary International's 1985 pledge to raise $120 million toward immunising all of the world's children against the disease. The last case of wild poliovirus poliomyelitis in the Americas was reported in Peru, August 1991.
On 20 August 1994 the Americas were certified as polio-free. This achievement was a milestone in efforts to eradicate the disease.
In 1995 Operation MECACAR (Mediterranean, Caucasus, Central Asian Republics and Russia) were launched; National Immunization Days were coordinated in 19 European and Mediterranean countries. In 1998, Melik Minas of Turkey became the last case of polio reported in Europe. In 1997 Mum Chanty of Cambodia became the last person to contract polio in the Indo-West Pacific region. In 2000 the Western Pacific Region (including China) was certified Polio-free.
In October 1999, the last isolation of type 2 poliovirus occurred in India. This type of poliovirus appears to have been eradicated.
Also in October 1999, The CORE Group—with funding from the United States Agency for International Development (USAID)—launched its effort to support national eradication efforts at the grassroots level. The CORE Group initiated this initiative in Bangladesh, India and Nepal in South Asia, and in Angola, Ethiopia and Uganda in Africa.
By 2001, 575 million children (almost one-tenth the world's population) had received some 2 billion doses of oral polio vaccine. The World Health Organization announced that Europe was polio-free on June 21, 2002, in the Copenhagen Glyptotek.
In 2002, an outbreak of polio occurred in India. The number of planned polio vaccination campaigns had recently been reduced, and populations in northern India, particularly from the Islamic background, engaged in mass resistance to immunization. At this time, the Indian state Uttar Pradesh accounted for nearly two-thirds of total worldwide cases reported. (See the 2002 Global polio incidence map.) However, by 2004, India had adopted strategies to increase ownership of polio vaccinations in marginalized populations, and the immunity gap in vulnerable groups rapidly closed.
In August 2003, rumors spread in some states in Nigeria, especially Kano, that the vaccine caused sterility in girls. This resulted in the suspension of immunization efforts in the state, causing a dramatic rise in polio rates in the already endemic country. On June 30, 2004, the WHO announced that after a 10-month ban on polio vaccinations, Kano had pledged to restart the campaign in early July. During the ban the virus spread across Nigeria and into 12 neighboring countries that had previously been polio-free. By 2006, this ban would be blamed for 1,500 children being paralyzed and had cost $450 million for emergency activities. In addition to the rumors of sterility and the ban by Nigeria's Kano state, civil war and internal strife in the Sudan and Côte d'Ivoire have complicated WHO's polio eradication goal. In 2004, almost two-thirds of all the polio cases in the world occurred in Nigeria (760 out of 1,170 total).
Eradication efforts in the Indian sub-continent have met with a large measure of success. Using the Pulse Polio campaign to increase polio immunization rates, India recorded just 66 cases in 2005, down from 135 cases reported in 2004, 225 in 2003, and 1,600 in 2002.
Yemen, Indonesia and Sudan, countries that had been declared polio-free since before 2000, each reported hundreds of cases—probably imported from Nigeria. On May 5, 2005, news reports broke that a new case of polio was diagnosed in Java, Indonesia, and the virus strain was suspected to be the same as the one that has caused outbreaks in Nigeria. New public fears over vaccine safety, which were unfounded, impeded vaccination efforts in Indonesia. In summer 2005 the WHO, UNICEF and the Indonesian government made new efforts to lay the fears to rest, recruiting celebrities and religious leaders in a publicity campaign to promote vaccination.
The first case of the polio outbreak in Sudan was detected in May 2004. The reemergence of polio led to stepped up vaccination campaigns. In the city of Darfur, 78,654 children were immunized and 20,432 more in southern Sudan (Yirol and Chelkou).
In the United States on September 29, 2005, the Minnesota Department of Health identified the first occurrence of vaccine derived polio virus (VDPV) transmission in the United States since OPV was discontinued in 2000. The poliovirus type 1 infection occurred in an unvaccinated, immunocompromised infant girl aged 7 months (the index patient) in an Amish community whose members predominantly were not vaccinated for polio.
In 2006 only four countries in the world (Nigeria, India, Pakistan and Afghanistan) were reported to have endemic poliomyelitis. Cases in other countries are attributed to importation. A total of 1,997 cases worldwide were reported in 2006; of these the majority (1,869 cases) occurred in countries with endemic polio. Nigeria accounted for the majority of cases (1,122 cases) but India reported more than ten times more cases this year than in 2005 (676 cases, or 30% of worldwide cases). Pakistan and Afghanistan reported 40 and 31 cases respectively in 2006. Polio re-surfaced in Bangladesh after nearly six years of absence with 18 new cases reported. "Our country is not safe, as neighbours India and Pakistan are not polio free", declared Health Minister ASM Matiur Rahman. (See: Map of reported polio cases in 2006)
In 2007 there were 1,315 cases of poliomyelitis reported worldwide. Over 60% of cases (874) occurred in India; while in Nigeria, the number of polio cases fell dramatically, from 1,122 cases reported in 2006 to 285 cases in 2007. Officials credit the drop in new infections to improved political control in the southern states and resumed immunisation in the north, where Muslim clerics led a boycott of vaccination in late 2003. Local governments and clerics allowed vaccinations to resume on the condition that the vaccines be manufactured in Indonesia, a majority Muslim country, and not in the United States. Turai Yar'Adua, wife of recently elected Nigerian president Umaru Yar'Adua, made the eradication of polio one of her priorities. Attending the launch of immunization campaigns in Birnin Kebbi in July 2007, Turai Yar'Adua urged parents to vaccinate their children and stressed the safety of oral polio vaccine.
In July 2007, a student traveling from Pakistan imported the first polio case to Australia in over 20 years. Other countries with significant numbers of wild polio virus cases include the Democratic Republic of the Congo, which reported 41 cases, Chad with 22 cases, and Niger and Myanmar, each of which reported 11 cases.
In 2008, 19 countries reported cases and the total number of cases was 1,652. Of these, 1,506 occurred in the four endemic countries and 146 elsewhere. The largest number were in Nigeria (799 cases) and India (559 cases): these two countries contributed 82.2 percent of all cases. Outside endemic countries Chad reported the greatest number (37 cases).
In 2009, a total of 1,606 cases were reported in 23 countries. 1,256 of these were in the four endemic countries, with the remaining 350 in 19 sub-Saharan countries with imported cases or re-established transmission. Once again, the largest number were in India (741) and Nigeria (388). All other countries had less than one hundred cases: Pakistan had 89 cases, Afghanistan 38, Chad 65, Sudan 45, Guinea 42, Angola 29, Côte d'Ivoire 26, Benin 20, Kenya 19, Niger 15, Central African Republic 14, Mauritania 13 and Sierra Leone and Liberia both had 11. The following countries had single digit numbers of cases: Burundi 2, Cameroon 3, the Democratic Republic of the Congo 3, Mali 2, Togo 6 and Uganda 8.
According to figures updated in April 2012, the World Health Organization reports that there were 1,352 cases of wild polio in 20 countries in 2010. Reported cases of polio were down 95% in Nigeria (to a historic low of 21 cases) and 94% in India (to a historic low of 42 cases) compared to the previous year, with little change in Afghanistan (from 38 to 25 cases) and an increase in cases in Pakistan (from 89 to 144 cases). 460 cases (34% of the global total) were reported from an acute outbreak in Tajikistan, which was associated with a further 18 cases across Central Asia (Kazakhstan and Turkmenistan) and the Russian Federation, with the most recent case from this region being reported from Russia the 25th September. These were the first cases in the WHO European region since 2002. 441 cases (30% of the global total) were reported from an outbreak in the Republic of Congo (Brazzaville). At least 179 deaths were associated with this outbreak, which is believed to have been an importation from the ongoing type 1 outbreak in Angola (33 cases in 2010) and the Democratic Republic of the Congo (100 cases).
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In 2011, cases were reported in the four endemic countries—Pakistan, Afghanistan, Nigeria and India—as well as in the Democratic Republic of Congo, Chad, Angola, Mali, Côte d'Ivoire, Burkina Faso, the Republic of Congo (Brazzaville), Niger, and Gabon. Almost 87 percent of all cases seen this year came from five countries: Pakistan, Chad, the Democratic Republic of the Congo, Afghanistan and Nigeria. In India, only 1 case of wild poliovirus was reported—a remarkable feat in a country that in many recent years has had a plurality or majority of the world's polio cases.
Since the start of 2010 there had been 14 outbreaks of polio, several continuing into 2011. Amid political instability, Côte d'Ivoire reported 36 cases of type 3 polio as part of an ongoing outbreak, with type 3 cases also in neighboring Mali and Guinea. Polio transmission recurred in Angola, Chad and the Democratic Republic of the Congo. Kenya reported its first case since 2009, while China reported 21 cases, mostly among the Xinjiang Uygur of Hotan prefecture, the first cases since 1994. Although the situation in Northern Nigeria improved, concerns exist about further outbreaks there because of its central location.
The situation in Pakistan is complex. The lowest number of cases reported in one year was 32 in 2007. In 2011, Pakistan reported 198 cases. The remaining focuses lie in three parts of Pakistan: Balochistan Province, Karachi and the Federally Administered Tribal Areas. About 25% of children in Karachi are unvaccinated against polio; in Balochistan ~50% are unvaccinated. In contrast in Afghanistan the unvaccinated rate is ~10%. The difficulty in Pakistan appears to be a lack of trust in the health workers trying to vaccinate the children, fueled partly by the CIA using fake vaccination campaigns as a cover to gather DNA samples from Osama Bin Laden's relatives.
At end of 2011 the WHO recorded a total of 650 cases worldwide. 310 of these were considered to be part of outbreaks. 16 countries recorded cases. Pakistan had the greatest number (198). Six other countries recorded numbers in double digits: Chad: 132 cases; Democratic Republic of Congo: 93; Afghanistan: 80; Nigeria: 61; Côte d'Ivoire: 36; and China: 21. The remaining countries were: Mali: 7; Angola: 5; Niger: 5; Central African Republic: 4; Guinea: 3; Congo: 1; Gabon: 1; India: 1; and Kenya: 1.
- Polio free
Several countries surpassed a year since their most recent reported case of polio. Most notably, the WHO reported that on January 13, India completed its first polio-free year and is now polio-free, leaving only three countries worldwide that have remained afflicted by endemic poliomyelitis. Other countries that in 2012 surpassed a year since a reported case the previous year were Gabon and Congo (January), Mali (June), Côte d'Ivoire, Angola and Kenya (July) and Guinea (August), China (October), and Central African Republic and the Democratic Republic of Congo (December). All those previously-infected countries did not report a case in 2012. Reported cases were limited to five countries, Nigeria, Pakistan, Afghanistan, Chad and Niger, four of which had fewer cases compared to 2011.
Nigeria remains the only polio-endemic country in Africa. By the end of the year, the number of confirmed cases in Nigeria was 122, of which 19 were type 3, well in excess of the 62 total cases reported in 2011. 90% of these cases were reported from eight persistently endemic northern states: Borno, Jigawa, Kano, Katsina, Kebbi, Sokoto, Yobe and Zamfara. The situation in northern Nigeria is complicated by ongoing security concerns, which are likely to hamper the polio eradication effort in this area. Nigeria also continues to represent the source of cases exported to neighboring countries.
Chad was one of only two non-endemic countries reporting polio cases in 2012, with 5 cases — all type 1. The last case was reported to have had onset on 14 June 2012. In 2011, Chad had reported 132 cases, representing a precipitous reduction in the Chad polio outbreak. A single instance of type 1 polio occurred in Niger in November. Characterization of the virus suggested importation from Nigeria, but it is thought to have circulated locally, undetected, for some time.
Pakistan remains the Asian country with the highest number of cases, but also has seen a significant reduction. By the end of 2012, 58 cases were reported, compared to 198 at the same time in 2011. Pakistan is the last remaining locus of type 3 outside Nigeria, having two reported cases, plus one type 1/3 hybrid. Two-thirds of all cases occurred in Balochistan and the Federally Administered Tribal Areas. In the previous year, 198 cases were reported, indicating an improvement in spite of July fatwas from several Pakistani Islamist groups prohibiting vaccination.
Afghanistan also saw a significant reduction in cases, with 37 cases reported by the end of the year, compared to 80 reported in 2011.
- End of year totals
The total number of wild-virus cases reported was 223. Of these Nigeria reported 122, Pakistan 58, Afghanistan 37, Chad 5 and Niger 1. Several additional countries, Chad, Democratic Republic of Congo, Somalia and Yemen, saw outbreaks of circulating vaccine-derived polio. In all there were 291 reported polio cases, the smallest number for any year on record.
Of the three countries in which polio is endemic, Pakistan, Afghanistan and Nigeria, the latter two have had significantly fewer cases in 2013 than reported by the same time the previous year. An ongoing outbreak centered on Bara in the Federally Administered Tribal Areas of Pakistan, where vaccination has been difficult, represents the major reservoir for the virus in Asia, affecting both Pakistan and neighboring Afghanistan, where there have been no cases in the tradition endemic region in the south. A growing outbreak in the Horn of Africa, centered in Banadir, Somalia, represents more than half of the year's total cases, the only wild cases in non-endemic countries reported in 2013. These have overwhelmed the gains made in endemic countries and by September the total number of polio cases surpassed that of the entire previous year. There have also been cases in Kenya, Ethiopia and Syria. By 26 November, 347 wild-virus cases had been reported, compared to 202 cases in 2012 reported by 27 November. Of these, cases in endemic countries have dropped from 197 to 123 while those in non-endemic countries have risen from 5 to 224. Circulating vaccine-derived cases have also been reported in the three endemic countries, as well as Somalia, Chad, Cameroon and Niger. India completed two years without a new polio case, needing one more year before it can be certified polio-free.
The sole remaining country in 2012 classified with reestablished transmission, Chad, has passed more than a year since its last wild-virus case, although it is still suffering from an outbreak of vaccine-derived virus. No type 3 cases have been reported in 2013. The last reported type 3 case of polio, world-wide, had its onset 11 November 2012 in Nigeria; the last wild case outside Nigeria was in April 2012 in Pakistan, and its absence from sewage monitoring in Pakistan suggests that active transmission of this strain has ceased there.
An ongoing outbreak centered on Bara in the Federally Administered Tribal Areas of Pakistan represents the major reservoir for the virus in Asia. Vaccination was banned by local leaders in North Waziristan from June, 2012, and the situation has been called alarming. It is also affecting neighboring Afghanistan. Major progress there has resulted in no reported cases in the tradition endemic region in the nation's south. Rather, all cases in Afghanistan in 2013 have been in the northeast and represent spillover from the Pakistani outbreak.
The year's biggest setback came in the Horn of Africa. Somalia had been free of wild polio since 2007 but had low levels of vaccination that put the nation at risk of reintroduction, and in April a case of polio in Mogadishu was found to be due to a wild polio strain of Nigerian origin. This came in spite of successful local negotiations the previous year that had allowed access to some populations for the first time in three years and a vigorous vaccination campaign already underway in this area, stricken by an outbreak of circulating vaccine-derived polio ongoing since 2011 that had also spread to neighboring Kenya and Yemen. The outbreak of wild polio spread to Dadaab, Kenya, home to a large camp hosting Somalian refugees. Intensive targeted vaccination efforts in both Mogadishu and Dadaab, as well as more broadly in Ethiopia, Djibouti and Yemen were instituted, but 48 cases caused by wild virus were reported in Somalia and Kenya by early July, and cases have begun to appear in south-central Somalia, where security considerations have compromised vaccination activities for three years. By October, over 170 cases had been reported in Somalia, with more than a dozen in Kenya and cases in the Somali Region of Ethiopia.
- Middle East
Routine sewage monitoring has revealed the virus in another region that had been polio-free. In late 2012, a PV1 virus strain of Pakistani origin was detected in Cairo, raising fears of reintroduction that sparked a major vaccination push in the city in 2013. No actual cases of polio were reported there, but the Cairo strain was later detected in Rahat, Israel in April 2013, and subsequently in Beer Sheba, Kiryat Gat and Ashdod. It has subsequently been detected across the country, indicating a prolonged, widespread transmission. Again, no cases of the disease have been found, and while a large-scale outbreak in Israel is thought unlikely due to their program of routine vaccination and high immunity levels, there is thought to be a moderate-to-high risk of further international spread.
In October and November, World Health Organization confirmed 17 cases of polio in Syria, where immunization rates have dropped significantly because of the civil war. As many as a dozen additional cases await confirmation. It was the first outbreak there in 14 years. DNA testing revealed the strain to be most closely related to that found in Egypt, and ultimately traces to Pakistan.
- Ongoing programme announcements
In late April, the WHO announced a new $5.5 billion, 6-year cooperative plan (called the 2013–18 Polio Eradication and Endgame Strategic Plan) to eradicate polio from its last reservoirs. The plan calls for mass immunization campaigns in the three remaining endemic countries. It also dictates a switch to inactivated virus injections, to avoid the risk of the vaccine-derived outbreaks that occasionally occur from use of the live-virus oral vaccine. In May, Bill Gates announced at the Global Vaccine Summit that total commitments to date stood at $4 billion or 73% of what is needed. This included pledges from Canada ($250 million), Britain ($457 million), Germany ($250 million), Norway ($240 million), Ireland ($6.65 million), Australia ($75.5 million), the Islamic Development Bank ($227 million) as well as the Gates foundation ($1.8 billion) and other philanthropists ($335 million).
On March 27, 2014, the WHO announced the eradication of poliomyelitis in the South-East Asia Region, in which the WHO includes eleven countries: Bangladesh, Bhutan, North Korea, India, Indonesia, Maldives, Myanmar, Nepal, Sri Lanka, Thailand and Timor-Leste. With the addition of this region, the proportion of world population living in polio-free regions has reached 80%. The last case of wild polio in the South-East Asia Region was reported in India on 13 January 2011.
Up to September 17, 178 cases of wild polio have been reported - compared to 264 in the same period last year, a 33% improvement. In the 3 endemic countries, Nigeria has reduced polio cases greatly from 47 to 6, Afghanistan increased to 8 from 4 and Pakistan greatly increased to 145 from 28. 19 cases have also been reported this year in non-endemic countries. 
- Eradication of infectious diseases
- Mathematical modelling of infectious disease
- Population health
- The Final Inch, a documentary film about the eradication effort
- Transmission risks and rates
- "Smallpox [Fact Sheet]". World Health Organization. Archived from the original on February 3, 2011. Retrieved November 9, 2013.
- "UN 'confident' disease has been wiped out". BBC News. 14 October 2010. Retrieved 14 October 2010.
- McNeil, Donald (February 1, 2011). "In Battle Against Polio, a Call for a Final Salvo". The New York Times. Retrieved 1 February 2011. "...getting rid of the last 1 percent has been like trying to squeeze Jell-O to death. As the vaccination fist closes in one country, the virus bursts out in another.... The [eradication] effort has now cost $9 billion, and each year consumes another $1 billion."
- Mahr, Krista (13 January 2013). "How India Fought Polio — and Won". TIME. Retrieved 28 February 2013.
- Polio’s Return After Near Eradication Prompts a Global Health Warning May 5, 2014 New York Times
- Barrett S (2004). "Eradication versus control: the economics of global infectious disease policies". Bull World Health Organ 82 (9): 683–8. PMC 2622975. PMID 15628206.
- Cockburn T (1961). "Eradication of infectious diseases". Science 133 (3458): 1050–8. Bibcode:1961Sci...133.1050C. doi:10.1126/science.133.3458.1050. PMID 13694225.
- [No authors listed] (1993). "Recommendations of the International Task Force for Disease Eradication". Morbidity and mortality weekly report 42 (RR-16): (RR–16):1–38. PMID 8145708. Retrieved 2007-04-13.
- General: Centers for Disease Control and Prevention. Global disease elimination and eradication as public health strategies. MMWR 1999;48(Suppl). Specific: Centers for Disease Control and Prevention. The Principles of Disease Elimination and Eradication. In: Global disease elimination and eradication as public health strategies. MMWR 1999;48(Suppl).
- World Health Organization (2003). Global polio eradication initiative: strategic plan 2004–2008 (PDF). Geneva: WHO. ISBN 92-4-159117-X.
- "Acute Flaccid Paralysis" (PDF). Public Health Notifiable Disease Management Guidelines. Alberta Government Health and Wellness. 2005. Retrieved 2007-07-31.[dead link]
- According to the United Nations Children's Fund (UNICEF) Supply Division. The price per dose of OPV is US$0.089–0.097.
- Paul J, Riordan J, Melnick J (1951). "Antibodies to three different antigenic types of poliomyelitis virus in sera from North Alaskan Eskimos". Am J Hyg 54 (2): 275–85. PMID 14877808.
- Mastny, Lisa (January 25, 1999). "Eradicating Polio: A Model for International Cooperation". Worldwatch Institute. Retrieved 2007-02-02.
- Robertson, Susan. (1993) The Immunological Basis for Immunization Series. Module 6: Poliomyelitis.[dead link] World Health Organization. Geneva, Switzerland.
- Nathanson N, Martin J (1979). "The epidemiology of poliomyelitis: enigmas surrounding its appearance, epidemicity, and disappearance". Am J Epidemiol 110 (6): 672–92. PMID 400274.
- Fine P (1993). "Herd immunity: history, theory, practice". Epidemiol Rev 15 (2): 265–302. PMID 8174658.
- Minor PD, Bel EJ (1990). Picornaviridae (excluding Rhinovirus). In: Topley & Wilson's Principles of Bacteriology, Virology and Immunity (volume 4) (8th ed.). London: Edward Arnold. pp. 324–357. ISBN 0-7131-4592-7.
- Atkinson W, Hamborsky J, McIntyre L, Wolfe S, eds. (2007). Epidemiology and Prevention of Vaccine-Preventable Diseases (The Pink Book) (PDF) (10th ed.). Washington, D.C.: Public Health Foundation. ISBN.
- Duintjer Tebbens R, Pallansch M, Kew O, Cáceres V, Sutter R, Thompson K (2005). "A dynamic model of poliomyelitis outbreaks: learning from the past to help inform the future". Am J Epidemiol 162 (4): 358–72. doi:10.1093/aje/kwi206. PMID 16014773.
- "Polio Eradication Evaluation". Retrieved 2008-02-19.[dead link]
- "Symptoms of Polio". NHS choices.
- "The disease and the virus". Global Polio Eradication Initiative. Retrieved 2010-04-27.[dead link]
- John F Maudlin. "The Bumpy Road to Polio Eradication". NEJM (362): 2346–2349.
- Imran Ali Teepu (26 February 2012). "WHO rejects polio rumours". Dawn. Retrieved 3 June 2012.
- Warraich HJ (2009). "Religious opposition to polio vaccination". Emerg Infect Dis 15 (6): 978. doi:10.3201/eid1506.090087. PMC 2727330. PMID 19523311.
- "Religious Opposition to Polio Vaccination - Volume 15, Number 6—June 2009 - Emerging Infectious Disease journal - CDC". C.cdc.gov. 2010-12-08. Retrieved 2014-03-29.
- Declan Walsh in Peshawar (2007-02-15). "Polio cases jump in Pakistan as clerics declare vaccination an American plot | World news". The Guardian. Retrieved 2014-03-29.
- Heidi Larson (27 May 2012). "The CIA's fake vaccination drive has damaged the battle against polio". The Guardian. Retrieved 3 June 2012.
- "Bin Laden death: 'CIA doctor' accused of treason". BBC News. 6 October 2011. Retrieved 8 October 2011.
- Imran Ali Teepu (2 March 2012). "American NGOs assail CIA over fake polio drive". Dawn. Retrieved 27 May 2012.
- Orla Guerin (24 May 2012). "'Emergency plan' to eradicate polio launched". BBC News. Retrieved 27 May 2012.
- Saeed Shah (2 March 2012). "CIA tactics to trap Bin Laden linked with polio crisis, say aid groups". The Guardian. Retrieved 27 May 2012.
- Gall C (2007-02-17). "Bomb Kills Doctor in Pakistani Border Area". The New York Times. Retrieved 2007-07-31.
- Declan Walsh (December 19, 2012). "U.N. Suspends Immunization Work in Pakistan". The New York Times. Retrieved December 19, 2012.
- Agence France-Presse: (2013-01-04). "Pakistan Resumes Polio Vaccines Under Tight Security". Reliefweb.int. Retrieved 2014-03-29.
- Associated Press in Peshawar (2013-01-29). "Gunmen kill police officer protecting polio workers in Pakistan". Guardian. Retrieved 2014-03-29.
- "Pakistan 'policeman killed' guarding anti-polio worker". Bbc.co.uk. 2013-02-26. Retrieved 2014-03-29.
- "Gunmen Attack Pakistani Polio Team, Kill Policeman". Rferl.org. 2013-05-20. Retrieved 2014-03-29.
- Mahsud, Sailab (2013-06-12). "Pakistani Villagers Vow 'No Electricity, No Polio Vaccinations'". Rferl.org. Retrieved 2014-03-29.
- 2 Polio Workers Killed in Pakistan
- "Nigeria polio vaccinators shot dead in Kano". Bbc.co.uk. 2013-02-08. Retrieved 2014-03-29.
- CBC News (14 May 2013). "Taliban pledge support for Afghan polio campaign". CBC News. Retrieved 18 May 2013.
- Pakistan polio workers shot dead in Karachi, BBC News, 21 January 2014
- "WHO Polio Case Count". Apps.who.int. 2014-03-13. Retrieved 2014-03-29.
- Due to the large increase in the number of vaccinators and field workers since 1998, the number of estimated cases is thought to be reasonably close to the actual reported number of cases in recent years. Aylward, Bruce, Jennifer Linkins. "Polio Eradication: mobilizing and managing the human resources". World Health Organization. Retrieved 2007-02-01.
- "Polio Case Count". World Health Organisation. 16 January 2014. Retrieved 24 January 2014.
- "PolioPlus Timeline". Rotary International. Retrieved 2011-03-11.[dead link]
- "Wild Poliovirus Weekly Update". Global Polio Eradication Initiative. Retrieved 2010-02-19.
- "WHO Vaccine Preventable Diseases: Monitoring system" (PDF). World Health Organization. 2006. Retrieved 2007-02-02.[dead link]
- Lee, Jong Wook (1995). "Ending polio – now or never?". The Progress of Nations. Unicef. Retrieved 2007-02-02.
- Slonim D (2005). "Global eradication of poliomyelitis. On the 80th anniversary of the founding of the National Institute of Health". Epidemiol Mikrobiol Imunol 54 (3): 99–108. PMID 16173520.
- Hinman A (1984). "Landmark perspective: Mass vaccination against polio". JAMA 251 (22): 2994–6. doi:10.1001/jama.251.22.2994. PMID 6371280.
- Fujimura SF (2005). "The Man Who Made Polio History". Pan American Health Organization. Retrieved 2007-02-02.
- "The End of Polio: Photographs of Sebastião Salgado Opens to Public" (Press release). Centers for Disease Control and Prevention. August 24, 2007. Retrieved 2008-06-02.
- Centers for Disease Control and Prevention (CDC) (1994). "International Notes Certification of Poliomyelitis Eradication – the Americas, 1994". Morbidity and Mortality Weekly Report (Centers for Disease Control and Prevention) 43 (39): 720–722. PMID 7522302.
- "Pulse Polio Programme". Government of India; Department of Family Welfare. 2013. Retrieved 2014-07-10.
- "Operation MECACAR". WHO Regional office for Europe. 2 June 2006. Archived from the original on 2007-07-29. Retrieved 2007-02-02.
- WHO Regional Office for Europe (2001-11-30). "WHO European Region celebrates three polio-free years: certification within reach in 2002". Press release 13/2001. Retrieved 2007-07-31.[dead link]
- Yamazaki, S.; Toraya, H. (2001). "(General News) Major Milestone reached in Global Polio Eradication: Western Pacific Region is certified Polio-Free". Health Educ. Res. 16 (1): 110. Bibcode:2001PDiff..16..110Y. doi:10.1154/1.1351153.
- "CORE Group Polio Eradication Initiative". Retrieved 2009-03-10.[dead link]
- "Europe achieves historic milestone as Region is declared polio-free". Press release (European Region of the World Health Organization). 21 June 2002. Retrieved 2007-02-02.[dead link]
- "WHO Director-General calls India 'number 1' polio eradication priority". News release. 2003-04-07. Retrieved 2007-07-31.
- Jegede, A. S. (2007). "What Led to the Nigerian Boycott of the Polio Vaccination Campaign?". PLoS Medicine 4 (3): e73. doi:10.1371/journal.pmed.0040073. PMC 1831725. PMID 17388657. Retrieved 1 June 2012.
- Balint-Kurti D (2005-05-04). "Polio Spreads From Nigeria After Claims". Associated Press. Retrieved 2013-01-19.
- Aglionby J (2005-09-02). "Indonesia faces polio challenge". Guardian Unlimited. Retrieved 2007-02-07.
- "Sudan: Bulletin No. 28". International Committee of the Red Cross (ICRC). 2005-05-11. Retrieved 2007-02-07.
- Bahta L, et al. (2005). "Poliovirus infections in four unvaccinated children—Minnesota, August–October 2005". MMWR Morb Mortal Wkly Rep 54 (41): 1053–5. PMID 16237378.
- "Bangladesh begins new polio drive". BBC News. 2007-03-02. Retrieved 2007-07-31.
- "First Lady of Nigeria inaugurates vaccination campaigns". The Global Polio Eradication Initiative. 30 July 2007. Archived from the original on 2007-12-09. Retrieved 2008-01-24.
- Yusufzai A (2007-07-30). "Pakistan polio case in Australia". BBC News. Retrieved 2007-08-08.
- "WHO Wild Poliovirus List". Retrieved 3 Feb 2013.
- Circulating vaccine-derived poliovirus (cVDPV) 2000–2013
- Global Polio Eradication Initiative Monthly Reports
- Arie S (2011) BMJ 343:d5465
- CIA organised fake vaccination drive to get Osama bin Laden's family DNA http://www.guardian.co.uk/world/2011/jul/11/cia-fake-vaccinations-osama-bin-ladens-dna
- "Global Polio Eradication Initiative > Data and monitoring > Polio this week". Polioeradication.org. Retrieved 2014-03-29.
- Thomson, William (7 February 2012). "India Winning Polio Fight". The Diplomat. Retrieved 24 April 2013.
- "Global Polio Eradication Initiative". Polioeradication.org. Retrieved 2014-03-29.
- Asif Choudary (2013-01-27). "Pakistan close to getting rid of a polio virus: WHO". Dawn.com. Retrieved 2014-03-29.
-  Ewen Callaway, "Somalia records its first wild polio case since 2007", Nature News Blog, 13 May 2013 (update 15 May)
- "Wild poliovirus in Kenya: Emergency response planned". Polioeradication.org. 2013-05-17. Retrieved 2014-03-29.
- Doucleff, Michaeleen (22 May 2013). "Polio Outbreak In Kenya: A Threat To Global Eradication". National Public Radio. Retrieved 27 May 2013.
- Polio in Somalia: UN warns of 'explosive' outbreak, BBC News, 16 August 2013
- McNeil Jr., Donald G. (23 January 2013). "Egypt: Polio Virus Is Found in Cairo’s Sewers". The New York Times. Retrieved 28 April 2013.
- http://www.npr.org/blogs/health/2013/04/26/178993960/a-5-5-billion-road-map-to-banish-polio-forever Jason Beaubien, "A $5.5 Billion Road Map To Banish Polio Forever", National Public Radio, 26 April 2013
- http://www.who.int/csr/don/2013_06_03/en/index.html "Poliovirus detected from environmental samples in Israel"
- Sterman, Adiv; Winer Jr., Stuart (12 June 2013). "More polio virus traces detected in Israel". Times of Israel. Retrieved 13 June 2013.
- McNeil Jr., Donald G. (7 June 2013). "Polio Virus Discovered in Sewage From Israel". The New York Times. Retrieved 3 June 2013.
- "Poliovirus detected from environmental samples in Israel – update". Who.int. 2013-07-15. Retrieved 2014-03-29.
- Syria polio outbreak confirmed by WHO, BBC News, 29 October 2013
- Cohen, Bryan (June 10, 2013). "Australia commits $75.5 million to end polio". VaccineNewsDaily. Retrieved 10 June 2013.
- "Global Vaccine Summit: The Roadmap to Polio Eradication". 20 May 2013. YouTube. Retrieved 13 June 2013.
- "WHO South-East Asia Region certified polio-free". WHO. 27 March 2014. Retrieved 27 March 2014.
- "Polio-free certification: WHO South-East Asia". WHO. 27 March 2014. Retrieved 27 March 2014.