Polio eradication

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A child receives oral polio vaccine during a 2002 campaign to immunize children in India.

A public health effort to permanently eliminate all cases of poliomyelitis (polio) infection around the world began in 1988, led by the World Health Organization (WHO), the United Nations Children's Fund (UNICEF) and the Rotary Foundation.[1] These organizations, along with the U.S. Centers for Disease Control and Prevention (CDC) and The Gates Foundation, have spearheaded the campaign through the Global Polio Eradication Initiative (GPEI). Successful eradication of infectious diseases has been achieved twice before, with smallpox[2] and bovine rinderpest.[3]

Prevention of disease spread is accomplished by vaccination. There are two kinds of polio vaccine—oral polio vaccine (OPV), which uses weakened poliovirus, and inactivated polio vaccine (IPV), which is injected. The OPV is less expensive and easier to administer, and can spread immunity beyond the person vaccinated, creating contact immunity. It has been the predominant vaccine used. However, under conditions of long-term vaccine virus circulation in under-vaccinated populations, mutations can reactivate the virus to produce a polio-inducing strain, while the OPV can also, in rare circumstances, induce polio or persistent asymptomatic infection in vaccinated individuals, particularly those that are immunodeficient. Being inactivated, the IPV is free of these risks but does not induce contact immunity. IPV is more costly and the logistics of delivery are more challenging.

The 33 diagnosed wild polio virus (WPV) cases worldwide in 2018 represented a 95% reduction from the 719 diagnosed cases in 2000 and a 99.99% reduction from the estimated 350,000 cases when the eradication effort began in 1988. Of the three strains of polio virus, the last recorded wild case caused by type 2 (WPV2) was in 1999, and WPV2 was declared eradicated in 2015. Type 3 (WPV3) is last known to have caused polio in 2012, and was declared eradicated in 2019.[4] All wild-virus cases since that date have been due to type 1 (WPV1). All three types are represented among the periodic cases arising from mutated oral vaccine strains, so-called circulating vaccine-derived poliovirus (cVDPV). India is the latest country to have officially stopped endemic transmission of polio, with its last reported case in 2011.[5] Three countries remain where the disease is still classified as endemic—Afghanistan, Pakistan and Nigeria.

Factors influencing eradication of polio[edit]

Eradication of polio has been defined in various ways—as elimination of the occurrence of poliomyelitis even in the absence of human intervention,[6] as extinction of poliovirus, such that the infectious agent no longer exists in nature or in the laboratory,[7] as control of an infection to the point at which transmission of the disease ceased within a specified area,[6] and as reduction of the worldwide incidence of poliomyelitis to zero as a result of deliberate efforts, and requiring no further control measures.[8]

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.[9]

Strategy[edit]

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. Several key strategies have been outlined for stopping polio transmission:[10]

  1. 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.
  2. Organization of "national immunization days" to provide supplementary doses of oral polio vaccine to all children less than five years old.
  3. Active surveillance for 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) among children less than fifteen years old. Other pathogenic agents can also cause AFP, such as enteroviruses, echoviruses, and adenoviruses.[11]
  4. Expanded environmental surveillance to detect the presence of poliovirus in communities.[12] Sewage samples are collected at regular and random sites and tested in laboratories for the presence of WPV or cVDPV. Since most polio infections are asymptomatic, transmission can occur in spite of the absence of polio-related AFP cases, and such monitoring helps to evaluate the degree to which virus continues to circulate in an area.
  5. Targeted "mop-up" campaigns once poliovirus transmission is limited to a specific focal area.

Vaccination[edit]

There are two distinct polio vaccines. The oral polio vaccine (OPV, or Sabin vaccine) contains an attenuated poliovirus, 10,000 times less able to enter the circulation and cause polio,[13] delivered as oral drops or infused into sugar cubes. It is highly effective and inexpensive (about US$0.12 per dose in 2016[13]) 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.[14] 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.[15][16] Due to its route of administration, it induces an immunization of the intestinal mucosa that protects against subsequent infection, though multiple doses are necessary to achieve effective prophylaxis.[13] It can also produce contact immunity. Attenuated poliovirus derived from the oral polio vaccine is excreted, and infects and indirectly induces immunity in unvaccinated individuals, thus amplifying the effects of the doses delivered.[17] The oral administration does not require special medical equipment or training. Taken together, these advantages have made it the preferred vaccine of many countries, and it has long been preferred by the global eradication initiative.[13]

The primary disadvantage of the OPV derives from its inherent nature as an attenuated but active virus. It can induce vaccine-associated paralytic poliomyelitis (VAPP) in approximately one individual per every 2.4 million doses administered.[18] Likewise, mutation during the course of persistent circulation in undervaccinated populations can lead to vaccine-derived poliovirus strains (cVDPV) that can induce polio at much higher rates.[18] Until recently, a trivalent OPV containing all three virus strains was used, but with the eradication of wild poliovirus type 2 this was phased out in 2016 and replaced with bivalent vaccine containing just types 1 and 3, while use of monovalent type 2 OPV is restricted to regions with documented cVDPV2 circulation.[13]

The inactivated polio vaccine (IPV, or Salk) contains trivalent fully inactivated virus, administered by injection. This vaccine cannot induce VAPP nor do cVDPV strains arise from it, but it likewise cannot induce contact immunity and thus must be administered to every individual. Added to this are greater logistical challenges. Though a single dose is sufficient for protection, administration requires medically trained vaccinators armed with single-use needles and syringes. Taken together, these factors result in substantially higher delivery costs.[19] Original protocols involved intramuscular injection in the arm or leg, but recently subcutaneous injection using a lower dose (so-called fractional-dose IPV, fIPV) has been found to be effective, lowering costs and also allowing for more convenient and cost-effective delivery systems.[20][21] The use of IPV results in serum immunity, but no intestinal immunity arises. As a consequence, a vaccinated individual is protected from contracting polio, but their intestinal mucosa can still be infected and serve as a reservoir for the excretion of live virus. For this reason, IPV is ineffective at halting ongoing outbreaks of WPV or cVDPV, but it has become the vaccine for choice for industrialized, polio-free countries.[19]

While IPV does not itself induce mucosal immunity, it has been shown to boost the mucosal immunity from OPV,[22] and WHO now favors a combined protocol. It is recommended that vulnerable children receive a dose of OPV at birth, then beginning at the age of 6 weeks a 'primary series' consisting of three OPV doses at least four weeks apart, along with one dose of IPV after 14 weeks.[18] This combined IPV/OPV approach has also been used in outbreak suppression.[23]

Herd immunity[edit]

Polio vaccination is also important in the development of herd immunity.[24] 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.[17] 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.[25]

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.[26]

Herd immunity is an important supplement to vaccination. Among those individuals who receive oral polio vaccine, only 95 percent will develop immunity after three doses.[27] 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.[24] 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.[24] If routine immunization were stopped, the number of unvaccinated, susceptible individuals would soon exceed the capability of herd immunity to protect them.[28]

Vaccine-derived poliovirus[edit]

Number of wild poliovirus cases, 1975–2017
(before 2000 may include small numbers of cVDPV cases)
Number of cVDPV cases, 2000-2018

While vaccination has played an instrumental role in the reduction of polio cases worldwide, the use of attenuated virus in the oral vaccine carries with it an inherent risk. The oral vaccine is a powerful tool in fighting polio in part because of its person-to-person transmission and resulting contact immunity. However, under conditions of long-term circulation in under-vaccinated populations, the virus can accumulate mutations that reverse the attenuation and result in vaccine virus strains that themselves cause polio. As a result of such circulating vaccine-derived poliovirus (cVDPV) strains, polio outbreaks have periodically recurred in regions that have long been free of the wild virus, but where vaccination rates have fallen. Oral vaccines can also give rise to persistent infection in immunodeficient individuals, with the virus eventually mutating into a more virulent immunodeficiency-associated vaccine-derived poliovirus (iVDPV). In particular the type 2 strain seems prone to reversions, so in 2016 the eradication effort abandoned the trivalent oral vaccine containing attenuated strains of all three virus types, and replaced it with a bivalent oral vaccine lacking the type 2 virus. Eradication efforts will eventually require all oral vaccination to be discontinued in favor of the use of injectable vaccines. These vaccines are more expensive and harder to deliver, and they lack the ability to induce contact immunity because they contain only killed virus, but they likewise are incapable of giving rise to vaccine-derived viral strains.[29][30]

Surveillance[edit]

A global program of surveillance for the presence of polio and the poliovirus plays a critical role in assessment of eradication and in outbreak detection and response. Two distinct methods are used in tandem: Acute Flaccid Paralysis (AFP) surveillance and environmental surveillance.[31]

Monitoring for AFP aims at identifying outbreaks of polio by screening patients displaying symptoms consistent with but not exclusive to severe poliovirus infection. Stool samples are collected from children presenting with AFP and evaluated for the presence of poliovirus by accredited laboratories in the Global Polio Laboratory Network. Since rates of non-polio AFP are expected to be constant and large compared to polio cases, the frequency of non-polio AFP reported in a population is indicative of the effectiveness of surveillance, as is the proportion of AFP patients from whom high-quality stool samples are collected and tested, with a target of at least 80%.[31]

Environmental surveillance is used to supplement AFP surveillance. This entails the routine testing of sewage samples for the presence of virus. This not only allows the effectiveness of vaccination efforts to be evaluated in countries with active transmission, but also allows the detection of new outbreaks in countries without known transmission. The GPEI currently[when?] conducts environmental surveillance in 44 countries, 24 of which are in Africa.[31]

Obstacles[edit]

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 potentially hostile intervention by outsiders. 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.[15]

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 and Uttar Pradesh states, 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.[32]

Two additional challenges are found in unobserved polio transmission and in vaccine-derived poliovirus. First, most polio infections are asymptomatic or result in minor symptoms, with less than 1% of infections leading to paralysis[33] and most infected people are unaware that they carry the disease, allowing polio to spread widely before cases are seen.[34] In 2000 using new screening techniques for the molecular characterization of outbreak viral strains, it was discovered that some of the outbreaks taking place were actually caused by circulating vaccine-derived poliovirus, following mutations or recombinations in the attenuated strain used for the oral polio vaccine. This altered the strategy envisioned for the discontinuation of vaccination following polio eradication,[35] necessitating an eventual switch to the more expensive and logistically more problematic inactivated polio vaccine, since continued use of the oral inactivated virus would continue to produce such revertant infection-causing strains.[36] The risk of vaccine-derived polio will persist long after the switch to inactivated vaccine, since a small number of chronic excretors continue to produce active virus for years (or even decades) after their initial exposure to the oral vaccine.[37]

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."[38]

Opposition to vaccination efforts[edit]

One factor contributing to the continued circulation of polio immunization programs has been opposition in some countries.[39]

In the context of the United States invasion of Afghanistan and the subsequent 2003 invasion of Iraq, rumours arose in the Muslim world that immunization campaigns were using intentionally-contaminated vaccines to sterilize local Muslim populations or to infect them with HIV. In Nigeria these rumours fit in with a longstanding suspicion of modern biomedicine, which since its introduction during the era of colonialism has been viewed as a projection of the power of western nations. Refusal of vaccination came to be viewed as resistance to western expansionism, and when the contamination rumours led the Nigerian Supreme Council for Sharia to call for a region-wide boycott of polio vaccination, polio cases in the country increased more than five-fold between 2002 and 2006, with the uncontrolled virus then spreading across Africa and globally.[40][41] In Afghanistan and Pakistan, fears that the vaccine contained contraceptives were one reason given by the Taliban in issuing fatwas against polio vaccination.[41][39][42] Skepticism in the Muslim world was exacerbated when it was learned in 2011 that the Central Intelligence Agency (CIA) had conducted a fake hepatitis B immunization campaign to collect blood samples from Osama bin Laden's Abbottabad compound in order to confirm the genetic identity of the children living there, and by implication his own presence, leading directly to his killing.[43][44] 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.[45] Pakistan reported the world's highest number of polio cases (198)[38][46] in 2011.[47] Religious boycotts based on contamination concerns have not been limited to the Muslim world. In 2015, after claiming that a tetanus vaccine contained a contraceptive, a group of Kenyan Catholic bishops called on their followers to boycott a planned round of polio vaccination. This did not have a major effect on vaccination rates, and dialog along with vaccine testing forestalled further boycott calls.[41]

Other religion-inspired refusals arise from concerns over whether the virus contains pig-derived products, and hence are haram (forbidden) in Islam,[48] prohibitions against taking of animal life that may be required for vaccine production,[41] or a resistance to interfering with divinely-directed disease processes.[40][41] Concerns were addressed through extensive outreach, directed both toward the communities involved and respected clerical bodies, as well as promoting local ownership of the eradication campaign in each region. 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".[38] Even with the express support of political leaders, polio workers or their accompanying security guards have been kidnapped, beaten, or assassinated.[39]

Polio vaccination efforts have also faced resistance in another form. The priority placed on vaccination by national authorities has turned it into a bargaining chip, with communities and interest groups resisting vaccination, not due to direct opposition, but to leverage other concessions from governmental authorities. In Nigeria this has taken the form of 'block rejection' of vaccination that is only resolved when state officials agree to repair or improve schools and health-care facilities, pave roads or install electricity.[49] There have been several instances of threatened boycotts by health workers in Pakistan over payment disputes.[50][51] Some governments have been accused of withholding vaccination or the necessary accompanying infrastructure from regions where opposition to their rule is high.[52]

Polio eradication criteria[edit]

A country is regarded as polio free or non-endemic if no cases have been detected for a year.[53][54] However, it is still possible polio circulates under these circumstances, as was the case for Nigeria, where a particular strain of virus resurfaced after five years in 2016.[55] This can be due to chance, limited surveillance and under-vaccinated populations.[56] Moreover, for the currently[when?] circulating virus WPV1, only 1 in 200 infection cases exhibit symptoms of polio paralysis in non-vaccinated children, and possibly even fewer in vaccinated children.[57] Therefore, even a single case is considered an epidemic.[58] According to modeling, it can take four to six months of no reported cases to achieve only a 50% chance of eradication, and one to two years for e.g. 95% chance.[56][57] Sensitivity of monitoring for circulation can be improved by sampling sewage. In Pakistan in the last couple of years, the number of paralysis cases has dropped relatively faster than the positive environmental samples, which has shown no progress since 2015. The presence of multiple infections with the same strain in the upstream area may not be detectable, so there are some saturation effects when monitoring the number of positive environmental samples.[59][60][61] Furthermore, virus may shed beyond the expected duration of several weeks in certain individuals. Contagiousness can not be readily excluded.[62] For a polio virus to be certified as eradicated worldwide, at least three years of good surveillance without cases needs to be achieved,[63] though this period may need to be longer for a strain like WPV3, where a lower proportion of those infected demonstrate symptoms, or if sewer samples stay positive.[64] Wild poliovirus type 2 was certified eradicated in 2015, the last case having been detected in 1999.[65] Wild poliovirus type 3 has not been detected since 2012, and was certified eradicated in 2019.

Timeline[edit]

International wild poliovirus cases by year
Year Estimated Recorded
1975 49,293[15]
...
1980 400,000[66] 52,552[15]
...
1985 38,637[15]
...
1988 350,000[67] 35,251[15]
...
1990 23,484[15]
...
1993 100,000[66] 10,487[15]
...
1995 7,035[15]
...
2000 719[68]
...
2005 1,979[68]
...
2010 1,352[68]
2011 650[68]
2012 223[68]
2013 416[68]
2014 359[68]
2015 74[68]
2016 37[68]
2017 22[69]
2018 33

Pre-1988[edit]

Kindergarten children receive a very early oral polio vaccine in 1960 in East Germany.

Following the widespread use of poliovirus vaccine in the mid-1950s, the incidence of poliomyelitis declined rapidly in many industrialized countries.[27] Czechoslovakia became the first country in the world to scientifically demonstrate nationwide eradication of poliomyelitis in 1960.[70] 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.[71] The Pan American Health Organization (PAHO), under the leadership of Ciro de Quadros, launched an initiative to eradicate polio from the Americas in 1985.[72]

Much of the work towards eradication was documented by Brazilian photographer Sebastião Salgado, as a UNICEF Goodwill Ambassador, in the book The End of Polio: Global Effort to End a Disease.[73]

1988–2000[edit]

In 1988, the World Health Organization (WHO) , together with Rotary International, UNICEF, and the U.S. Centers for Disease Control and Prevention (CDC) 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.[72] The last case of wild poliovirus poliomyelitis in the Americas was reported in Peru, August 1991.[72]

On 20 August 1994. the Americas were certified as polio-free.[74] This achievement was a milestone in efforts to eradicate the disease.

In 1994, the Indian Government launched the Pulse Polio Campaign to eliminate polio. The current[when?] campaign involves annual vaccination of all children under age five.[75]

In 1995 Operation MECACAR (Mediterranean, Caucasus, Central Asian Republics and Russia) were launched; National Immunization Days were coordinated in 19 European and Mediterranean countries.[76] In 1998, Melik Minas of Turkey became the last case of polio reported in Europe.[77] In 1997, Mum Chanty of Cambodia became the last person to contract polio in the Indo-West Pacific region.[78] In 2000 the Western Pacific Region (including China) was certified polio-free.[78]

In October 1999, the last isolation of type 2 poliovirus occurred in India. This type of poliovirus was declared eradicated.[27][79]

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.[80]

2001–2005[edit]

Disability-adjusted life year for poliomyelitis per 100,000 inhabitants in 2004

By 2001, 575 million children (almost one-tenth the world's population) had received some two billion doses of oral polio vaccine.[81] The World Health Organization announced that Europe was polio-free on 21 June 2002, in the Copenhagen Glyptotek.[82]

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.[83] (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.[citation needed]

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.[84] On 30 June 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.[72] 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).[citation needed]

Countries with polio cases in 2005

In May 2004 the first case of the polio outbreak in Sudan was detected. 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).[85]

In 2005 there were 1,979 cases of wild poliovirus (excludes vaccine-derived polio viruses).[86] Most cases were located in two areas: the Indian subcontinent and Nigeria. Eradication efforts in the Indian sub-continent 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.[87]

Yemen, Indonesia and Sudan, countries that had been declared polio-free since before 2000, each reported hundreds of cases—probably imported from Nigeria.[88] On 5 May 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.[89]

In the United States on 29 September 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 seven months (the index patient) in an Amish community whose members predominantly were not vaccinated for polio.[90]

2006–2010[edit]

In 2006, only four countries in the world (Nigeria, India, Pakistan and Afghanistan) were reported to have endemic polio. 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.[86] 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.[91] (See: Map of reported polio cases in 2006)

In 2007, there were 1,315 cases of poliomyelitis reported worldwide.[86] 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.[88] 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.[92]

In July 2007, a student traveling from Pakistan imported the first polio case to Australia in over 20 years.[93] 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.[86]

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).[86]

In 2009, a total of 1,606 cases were reported in 23 countries. Four endemic countries accounted for 1,256 of these, 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).[86] 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 WHO reported 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). An acute outbreak in Tajikistan gave rise to 460 cases (34% of the global total), and 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 25 September. These were the first cases in the WHO European region since 2002. The Republic of Congo (Brazzaville) saw an outbreak with 441 cases (30% of the global total). 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).[86][94]

2011–2015[edit]

In 2011, 650 WPV cases were reported in sixteen countries: the four endemic countries—Pakistan, Afghanistan, Nigeria and India—as well as twelve others. 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 Uyghurs of Hotan prefecture, Xinjiang, the first cases since 1994.[citation needed]

The total number of wild-virus cases reported in 2012 was 223, lower than any previous year. These were limited to five countries—Nigeria, Pakistan, Afghanistan, Chad, and Niger—of which all except Nigeria had fewer cases than in 2011.[95] Several additional countries, Chad, Democratic Republic of the Congo, Somalia and Yemen, saw outbreaks of circulating vaccine-derived polio. The last reported type 3 case of polio worldwide had its onset 11 November 2012 in Nigeria; the last wild case outside Nigeria was in April 2012 in Pakistan,[95] and its absence from sewage monitoring in Pakistan suggests that active transmission of this strain has ceased there.[96] A total of 416 wild-virus cases were reported in 2013, almost double the previous year. Of these, cases in endemic countries dropped from 197 to 160, while those in non-endemic countries jumped from 5 to 256 owing to two outbreaks: one in the Horn of Africa, and one in Syria.

In April, a case of wild polio in Mogadishu was reported, the first in Somalia since 2007.[97] By October, over 170 cases had been reported in the country,[98] with more cases in neighboring Kenya and the Somali Region of Ethiopia.

Routine sewage monitoring in 2012 had detected a WPV1 strain of Pakistani origin in Cairo, sparking a major vaccination push there.[99] The strain spread to Israel, where there was widespread environmental detection, but like Egypt, no paralysis cases.[100][101][102] It had more severe consequences when it spread to neighboring Syria, with the total number of cases eventually reaching 35, the first outbreak there since 1999.[103][104]

In April 2013, 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 called for mass immunization campaigns in the three remaining endemic countries, and also dictated 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.[105]

In 2014, there were 359 reported cases of wild poliomyelitis, spread over twelve countries. Pakistan had the most with 306, an increase from 93 in 2013, which was blamed on Al Qaeda and Taliban militants preventing aid workers from vaccinating children in rural regions of the country.[106][107][108] On 27 March 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.[109] With the addition of this region, the proportion of world population living in polio-free regions reached 80%.[109] The last case of wild polio in the South-East Asia Region was reported in India on 13 January 2011.[110]

During 2015, 74 cases of wild poliomyelitis were reported worldwide, 54 in Pakistan and 20 in Afghanistan. There were 32 circulating vaccine-derived poliovirus (cVDPV) cases in 2015.[111][112]

On 25 September 2015, the WHO declared that Nigeria was no longer considered endemic for wild polio virus,[53] with no reported case of wild polio virus having been reported since 24 July 2014.[95] A WPV1 strain not seen in five years resurfaced in Nigeria the following year.[55]

The WPV2 virus was declared eradicated in September 2015 as it had not been detected in circulation since 1999[79] and WPV3 was declared eradicated in October 2019,[113] having last been detected in 2012. Both types persist in the form of circulating vaccine-derived strains, the product of years-long evolution of transmissible oral vaccine in under-immunized populations.

Reported polio cases in 2011[114]
Polio worldwide 2011.svg
Country Wild
cases
Circulating
vaccine-
derived
cases
Transmission
status
 Pakistan 198 0 endemic
 Chad 132 0 re-established
 DRC 93 11 importation
 Afghanistan 80 1 endemic
 Nigeria 62 33 endemic
 Côte d'Ivoire 36 0 importation
 China 21 0 importation
 Mali 7 0 importation
 Angola 5 0 re-established
 Niger 5 1 importation
 Central African Republic 4 0 importation
 Guinea 3 0 importation
 Republic of the Congo 1 0 importation
 Gabon 1 0 importation
 India 1 0 endemic
 Kenya 1 0 importation
 Somalia 0 9 cVDPV only
 Yemen 0 9 cVDPV only
 Mozambique 0 2 cVDPV only
Total 650 66
Reported polio cases in 2012[114]
Polio worldwide 2012.svg
Country Wild
cases
Circulating
Vaccine-
derived
cases
Transmission
Status
 Nigeria 122 9 endemic
 Pakistan 58 16 endemic
 Afghanistan 37 9 endemic
 Chad 5 12 re-established
 Niger 1 0 importation
 DRC 0 17 cVDPV only
 Kenya 0 3 cVDPV only
 Yemen 0 2 cVDPV only
 China 0 2 cVDPV only
 Somalia 0 1 cVDPV only
Total 223 71
Reported polio cases in 2013[114]
Polio worldwide 2013.svg
Country Wild
cases
Circulating
vaccine-
derived
cases
Transmission
status
 Somalia 194 1 importation
 Pakistan 93 48 endemic
 Nigeria 53 4 endemic
 Syria 35 0 importation
 Afghanistan 14 3 endemic
 Kenya 14 0 importation
 Ethiopia 9 0 importation
 Cameroon 4 4 importation
 Chad 0 3 cVDPV only
 Yemen 0 1 cVDPV only
 Niger 0 1 cVDPV only
Total 416 65
Reported polio cases in 2014[114]
Polio worldwide 2014.svg
Country Wild
cases
Circulating
vaccine-
derived
cases
Transmission
status
 Pakistan 306 22 endemic
 Afghanistan 28 0 endemic
 Nigeria 6 30 endemic
 Cameroon 5 0 importation
 Equatorial Guinea 5 0 importation
 Somalia 5 0 importation
 Iraq 2 0 importation
 Ethiopia 1 0 importation
 Syria 1 0 importation
 South Sudan 0 2 cVDPV only
 Guinea 0 1 cVDPV only
 Madagascar 0 1 cVDPV only
Total 359 56
Reported polio cases in 2015[114]
Polio worldwide 2015.svg
Country Wild
cases
Circulating
vaccine-
derived
cases
Transmission
status
Type(s)
 Pakistan 54 2 endemic WPV1
cVDPV2
 Afghanistan 20 0 endemic WPV1
 Madagascar 0 10 cVDPV only cVDPV1
 Laos 0 8 cVDPV only cVDPV1
 Guinea 0 7 cVDPV only cVDPV2
 Ukraine 0 2 cVDPV only cVDPV1
 Myanmar 0 2 cVDPV only cVDPV2
 Nigeria 0 1 cVDPV only cVDPV2
Total 74 32

2016[edit]

Reported polio cases in 2016[114]
Polio worldwide 2016.svg
Country Wild
cases
Circulating
vaccine-
derived
cases
Transmission
status
Type(s)
 Pakistan 20 1 endemic WPV1
cVDPV2
 Afghanistan 13 0 endemic WPV1
 Nigeria 4 1 endemic WPV1
cVDPV2
 Laos 0 3 cVDPV only cVDPV1
Total 37 5

There were 37 reported WPV1 cases with an onset of paralysis in 2016, half as many as in 2015. Twenty of these cases occurred in Pakistan, thirteen in Afghanistan, and four in Nigeria.[115] The cases of WPV1 in Nigeria were viewed as a setback, there having been no detected cases caused by the wild virus there in almost two years, yet genetic analysis showed that the virus was of a strain circulating undetected since 2011 in regions inaccessible due to the activities of Boko Haram.[55][116]

The 2015 cVDPV1 outbreak in Laos continued into 2016, with three cases in January.[117] Two separate strains of cVDPV2 were reported in Nigeria's Borno and Sekoto states, the latter resulting in one case. In Pakistan a new strain of cVDPV2 arose in the Quetta area, with one instance of paralysis.[118][119]

Environmental samples from Hyderabad, India from January 2015 to May 2016 showed the ongoing presence of a cVDPV2 strain in that city, without diagnosed cases.[120] Due to shortages in the global supply of injectable vaccine, an emergency campaign was launched using vaccine at one fifth the normal dose (fractional-Dose Inactivated Polio Vaccine, or fIPV), the first mass vaccination using this dosage of injectable vaccine.[20]

Attacks on polio vaccination campaigns continued. A suicide bombing in Quetta in January and a pair of attacks by gunmen in Karachi in April targeted Pakistani security personnel protecting vaccinators,[121][122] while in January three Afghan vaccination workers disappeared and their bodies were found weeks later.[123]

Because cVDPV2 strains continued to arise from trivalent oral vaccine that included attenuated WPV2, in April and May 2016 this vaccine was replaced with a bivalent version lacking WPV2 as well as trivalent injected inactivated vaccine that cannot lead to cVDPV cases. This is expected to prevent new strains of cVDPV2 from arising and allow eventual cessation of WPV2 vaccination.[124]

2017[edit]

Reported polio cases in 2017[114]
Polio worldwide 2017.svg
Country Wild
cases
Circulating
vaccine-
derived
cases
Transmission
status
Type(s)
 Afghanistan 14 0 endemic WPV1
 Pakistan 8 0 endemic WPV1
 DRC 0 22 cVDPV only cVDPV2
 Syria 0 74 cVDPV only cVDPV2
Total 22 96

There were 22 reported WPV1 polio cases with onset of paralysis in 2017, down from 37 in 2016. Eight of the cases were in Pakistan and 14 in Afghanistan,[69] where genetic typing showed repeated introduction from Pakistan as well as local transmission.[125] In Pakistan, transmission of several genetic lineages of WPV1 seen in 2015 had been interrupted by September 2017, though at least two genetic clusters remain. In spite of a significant drop in detected cases in Pakistan, there was an increase in the percentage of environmental samples that test positive for the polio virus, suggesting gaps in identification of infected individuals.[126][127] In the third country where polio remains endemic, Nigeria, there were no cases, though as few as 7% of infants were fully vaccinated in some districts.[128][129] An April 2017 spill at a vaccine production facility in the Netherlands only resulted in one asymptomatic WPV2 infection, despite release into the sewer system.[130]

Laos was declared free of cVDPV1 in March,[54][131] but three distinct cVDPV2 outbreaks occurred in the Democratic Republic of the Congo, one of them or recent origin, the other two having circulated undetected for more than a year. Together they caused 20 cases by year's end.[132][133][134][135] In Syria a large outbreak began at Mayadin, Deir ez-Zor Governorate, a center of fighting in the Syrian Civil War and also spreading to neighboring districts saw 74 confirmed cases from a viral strain that had circulated undetected for about two years.[136][137] Circulation of multiple genetic lines of cVDPV2 was also detected in Banadir province, Somalia, but no infected individuals were identified.[138] WHO's Strategic Advisory Group of Experts on Immunization recommended that cVDPV2 suppression be prioritized over targeting WPV1,[139] and according to protocol OPV2 is restricted to this purpose.

The 2016 global switch in vaccination methods resulted in shortages of the injectable vaccine,[140] and led the WHO in April 2017 to recommend general use of the fIPV vaccination protocol, involving subcutaneous injection of a lower dose than used in the standard intramuscular delivery.[141]

2018[edit]

Reported polio cases in 2018[142]
Polio worldwide 2018.svg
Country Wild
cases
Circulating
vaccine-
derived
cases
Transmission
status
Type
 Afghanistan 21 0 endemic WPV1
 Pakistan 12 0 endemic WPV1
 Nigeria 0 34 cVDPV only cVDPV2
 Papua New Guinea 0 26 cVDPV only cVDPV1
 DRC 0 20 cVDPV only cVDPV2
 Somalia 0 12 cVDPV only cVDPV2
cVDPV3
 Niger 0 10 cVDPV only cVDPV2
 Indonesia 0 1 cVDPV only cVDPV1
 Mozambique 0 1 cVDPV only cVDPV2
Total 33 104

There were 33 reported WPV1 paralysis cases with an onset of paralysis in 2018 – 21 in Afghanistan and 12 in Pakistan.[128][143] In Pakistan, three of the cases occurred in Kohlu District in Balochistan, with eight in Khyber Pakhtunkhwa, and one in the greater Karachi area, Sindh.[142][144] Viral circulation across much of the country, including several major urban areas, led to wild poliovirus detection in 20% of the year's environmental samples.[145] The rates of parental refusal for vaccination are increasing.[146] Cases in Afghanistan represented two transmission clusters, one in Kandahar, Urozgan and Helmand Provinces in the south, the other in the adjacent Nuristan, Kunar and Nangarhar Provinces in the northeast, on the Pakistani border.[147][148] Virus involved in several Afghanistan cases had a closest relative in Pakistan, suggesting significant trans-border spread, but the majority represented spread within Afghanistan. Some of these were caused by so-called 'orphan' strains, resulting from long undetected transmission and indicating gaps in monitoring. Different strains were largely responsible for the cases in the northwest and south of the country.[149] Nigeria, the third country classified as having endemic transmission, passed two full years without a detected wild-virus case,[citation needed] but security concerns continued to limit access to some areas of the country and elimination of WPV transmission could not be confirmed.[citation needed]

Cases caused by vaccine-derived poliovirus were reported in seven countries, with more than 100 total cases. Surveillance detected nine strains of cVDPV in 2018 in seven countries.[31] In the Democratic Republic of Congo, one of the outbreaks of cVDPV2 first detected in 2017 caused no additional cases, but suppression of the other two with OPV2 proved insufficient: not only did they continue, but the vaccination efforts gave rise to a novel cVDPV2 outbreak.[135] The country experienced a total of 20 cases in 2018.[134][142] Two separate cVDPV2 outbreaks in northern Nigeria produced 34 cases,[142][150] as well as giving rise to 10 cases in the neighboring Niger. In Somalia, cVDPV2 continued to circulate, causing several polio cases and detected in environmental samples from as far as Nairobi, Kenya. This virus, along with newly-detected cVDPV3, caused twelve total cases in the country, including one patient infected by both strains.[138][142][151] The large number of children residing in areas inaccessible to health workers represent a particular risk for undetected cVDPV outbreaks.[135] A cVDPV2 outbreak in Mozambique also resulted in a single case.[142][152] Response to the Syrian cVDPV2 outbreak continued into 2018, and virus transmission was successfully interrupted.[153] In Papua New Guinea, a cVDPV1 strain arose, causing twenty-six polio cases across nine provinces,[154] while a single diagnosed cVDPV1 case in neighboring Western New Guinea, Indonesia, resulted from a distinct outbreak.[142]

2019[edit]

Reported polio cases in 2019[142]
Polio worldwide 2019.svg
Country Wild
cases
Circulating
vaccine-
derived
cases
Transmission
status
Type
 Pakistan 82 7 endemic WPV1
cVDPV2
 Afghanistan 20 0 endemic WPV1
 DRC 0 42 cVDPV only cVDPV2
 Angola 0 41 cVDPV only cVDPV2
 Nigeria 0 17 cVDPV only cVDPV2
 CAR 0 14 cVDPV only cVDPV2
 Myanmar 0 6 cVDPV only cVDPV1
 Ghana 0 5 cVDPV only cVDPV2
 Ethiopia 0 3 cVDPV only cVDPV2
 Philippines 0 3 cVDPV only cVDPV2
 Somalia 0 3 cVDPV only cVDPV2
 Benin 0 2 cVDPV only cVDPV2
 Chad 0 1 cVDPV only cVDPV2
 China 0 1 cVDPV only cVDPV2
 Niger 0 1 cVDPV only cVDPV2
 Togo 0 1 cVDPV only cVDPV2
 Zambia 0 1 cVDPV only cVDPV2
Total 102 148

As of 13 November, 102 WPV1 paralysis cases had been detected in 2019: 20 in Afghanistan and 82 in Pakistan.[142][155] In particular, in Pakistan the number of cases is surging.[156][157] Transborder migration continues to play a role in polio transmission in the two countries.[158][159] While problematic, this has fostered a dangerous false-narrative in both nations, blaming the other for the presence and spread of polio in their own country.[160] Environmental sampling in Pakistan has recently shown the virus' presence in eight urban areas, a setback officials attribute primarily to vaccine refusal.[161] Opponents to vaccination in Pakistan launched a series of attacks in April that left a vaccinator and two security men dead, while false rumors and hoax videos reporting vaccine toxicity have also disrupted vaccination efforts there.[157][162] Wild poliovirus has also been detected in several environmental samples in Iran, but no resulting polio cases have been diagnosed.[155] The Iranian virus is linked genetically to a poliovirus strain from Karachi, Pakistan.[163] In the third remaining country in which polio is considered endemic, Nigeria, wild poliovirus has not been detected since October 2016, and levels of AFP surveillance are sufficient, even in security-compromised regions, to suggest transmission of WPV may have been interrupted.[164] WPV3 eradication was certified in October 2019, having not been seen since 2012.[165]

There have been more than 100 cases caused by cVDPV, as of 13 November 2019.[142] The cVDPV2 outbreaks in Nigeria, the Democratic Republic of Congo, and Somalia continued into 2019 and spread to neighboring countries, while several countries have experienced new outbreaks.[166] In addition to sixteen reported paralysis cases in Nigeria, the cVDPV2 outbreaks there have spread to Ghana, Benin, Chad, Niger and Togo, while the virus has also been detected in environmental samples from Cameroon and Ivory Coast. Somalia's continuing outbreaks have caused a half-dozen cases there and in Ethiopia. The Democratic Republic of Congo has had numerous new and continuing outbreaks, producing dozens of cases, while multiple new cVDPV2 outbreaks have resulted in dozens of cases in Angola and the Central African Republic.[167] Individual new outbreaks of cVDPV2 have also caused paralysis cases in China,[142] Pakistan,[142] the Philippines,[168][169] and Zambia.[142] There have also been two outbreaks of cVDPV1, in Myanmar where one caused six cases,[142] and in the Philippines, where a separate outbreak has been detected in environmental samples but there have been no reported cases.[170]

See also[edit]

References[edit]

  1. ^ "Polio Eradication | Global Health Strategies". Global Health Strategies. Archived from the original on 8 March 2016. Retrieved 11 February 2016.
  2. ^ "Smallpox [Fact Sheet]". World Health Organization (WHO). Archived from the original on 3 February 2011. Retrieved 9 November 2013.
  3. ^ Ghosh P (14 October 2010). "Rinderpest virus has been wiped out, scientists say". BBC News Online. Retrieved 14 October 2010.
  4. ^ "GPEI-Two out of three wild poliovirus strains eradicated". Retrieved 2 November 2019.
  5. ^ Mahr K (13 January 2013). "How India Fought Polio — and Won". Time. Retrieved 28 February 2013.
  6. ^ a b Barrett S (2004). "Eradication versus control: the economics of global infectious disease policies" (PDF). Bull World Health Organ. 82 (9): 683–8. hdl:10665/269225. ISSN 0042-9686. PMC 2622975. PMID 15628206.
  7. ^ Cockburn TA (April 1961). "Eradication of infectious diseases". Science. 133 (3458): 1050–8. Bibcode:1961Sci...133.1050C. doi:10.1126/science.133.3458.1050. PMID 13694225.
  8. ^ Centers for Disease Control and Prevention (December 1993). "Recommendations of the International Task Force for Disease Eradication" (PDF). MMWR Recommendations and Reports. 42 (RR-16): 1–38. PMID 8145708.
  9. ^ Centers for Disease Control and Prevention (December 1999). "Global Disease Elimination and Eradication as Public Health Strategies. Proceedings of a conference. Atlanta, Georgia, USA. 23-25 February 1998" (PDF). MMWR Supplement. 48: 1–208. PMID 11186140.
  10. ^ Global Polio Eradication Initiative, World Health Organization (2003). Global polio eradication initiative: strategic plan 2004–2008 (PDF). Geneva: World Health Organization (WHO). hdl:10665/42850. ISBN 978-92-4-159117-1.
  11. ^ "Acute Flaccid Paralysis (AFP)". Public Health Notifiable Disease Management Guidelines. Alberta Government Health and Wellness. 2018. Retrieved 28 October 2019.
  12. ^ Global Polio Eradication Initiative, World Health Organization (April 2015). Polio environmental surveillance expansion plan: global expansion plan under the endgame strategy 2013-2018 (PDF) (Report). World Health Organization (WHO). hdl:10665/276245. WHO/POLIO/15.02. Retrieved 1 July 2018.
  13. ^ a b c d e "OPV". Global Polio Eradication Initiative (GPEI). Retrieved 7 July 2018.
  14. ^ 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. doi:10.1093/oxfordjournals.aje.a119485. PMID 14877808.
  15. ^ a b c d e f g h i Mastny L (25 January 1999). "Eradicating Polio: A Model for International Cooperation". Worldwatch Institute. Archived from the original on 8 June 2006. Retrieved 2 February 2007.
  16. ^ Robertson, Susan. (1993) The Immunological Basis for Immunization Series. Module 6: Poliomyelitis. World Health Organization. Geneva, Switzerland.
  17. ^ a b Nathanson N, Martin J (1979). "The epidemiology of poliomyelitis: enigmas surrounding its appearance, epidemicity, and disappearance". Am J Epidemiol. 110 (6): 672–92. doi:10.1093/oxfordjournals.aje.a112848. PMID 400274.
  18. ^ a b c "International travel and health: Poliomyelitis (Polio)". World Health Organization (WHO). Retrieved 7 July 2018.
  19. ^ a b "IPV". Global Polio Eradication Initiative (GPEI). Retrieved 7 July 2018.
  20. ^ a b Bahl S, Verma H, Bhatnagar P, Haldar P, Satapathy A, Kumar KN, Horton J, Estivariz CF, Anand A, Sutter R (August 2016). "Fractional-Dose Inactivated Poliovirus Vaccine Immunization Campaign - Telangana State, India, June 2016" (PDF). Morbidity and Mortality Weekly Report (MMWR). 65 (33): 859–63. doi:10.15585/mmwr.mm6533a5. PMID 27559683.
  21. ^ Hiromasa Okayasu; Carolyn Sein; Diana Chang Blanc; Alejandro Ramirez Gonzalez; Darin Zehrung; Courtney Jarrahian; Grace Macklin; Roland W. Sutter (2017). "Intradermal Administration of Fractional Doses of Inactivated Poliovirus Vaccine: A Dose-Sparing Option for Polio Immunization" (PDF). The Journal of Infectious Diseases. 216 (S1): S161–7. doi:10.1093/infdis/jix038. PMC 5853966. PMID 28838185.
  22. ^ Edward P K Parker; Natalie A Molodecky; Margarita Pons-Salort; Kathleen M O'Reilly; Nicholas C Grassly (2015). "Impact of inactivated poliovirus vaccine on mucosal immunity: implications for the polio eradication endgame". Expert Review of Vaccines. 14 (8): 1113–1123. doi:10.1586/14760584.2015.1052800. PMC 4673562. PMID 26159938.
  23. ^ Branswell H (20 March 2014). "Combination of oral, injectable polio vaccine used for first time in outbreak". CTV. Retrieved 7 July 2018.
  24. ^ a b c Fine P (1993). "Herd immunity: history, theory, practice". Epidemiol Rev. 15 (2): 265–302. doi:10.1093/oxfordjournals.epirev.a036121. PMID 8174658.
  25. ^ Shaw L, Spears W, Billings L, Maxim P (October 2010). "Effective Vaccination Policies". Information Sciences. 180 (19): 3728–3744. doi:10.1016/j.ins.2010.06.005. ISSN 0020-0255. PMC 2967767. PMID 21057602.
  26. ^ Minor PD, Bel EJ (1990). Picornaviridae (excluding Rhinovirus). In: Topley & Wilson's Principles of Bacteriology, Virology and Immunity (volume 4) (8th ed.). London: Arnold. pp. 324–357. ISBN 978-0-7131-4592-2. OCLC 32823271.
  27. ^ a b c Centers for Disease Control and Prevention (2015). Hamborsky J, Kroger A, Wolfe S (eds.). Epidemiology and Prevention of Vaccine-Preventable Diseases (PDF) (13th ed.). Washington, D.C.: Public Health Foundation. ISBN 978-0990449119.
  28. ^ 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.
  29. ^ "Vaccine-Derived Poliovirus". Global Polio Eradication Initiative (GPEI). Retrieved 26 June 2018.
  30. ^ Duintjer Tebbens, Duintjer Tebbens RJ, Thompson KM (September 2015). "Managing the risk of circulating vaccine-derived poliovirus during the endgame: oral poliovirus vaccine needs". BMC Infectious Diseases. 15: 390. doi:10.1186/s12879-015-1114-6. PMC 4582727. PMID 26404780.
  31. ^ a b c d Patel JC, Diop OM, Gardner T, Chavan S, Jorba J, Wassilak SG, Ahmed J, Snider CJ (April 2019). "Surveillance to Track Progress Toward Polio Eradication - Worldwide, 2017-2018" (PDF). Morbidity and Mortality Weekly Report (MMWR). 68 (13): 312–318. doi:10.15585/mmwr.mm6813a4. PMC 6611474. PMID 30946737.
  32. ^ "Polio Eradication Evaluation". Archived from the original on 6 July 2010. Retrieved 19 February 2008.
  33. ^ "Poliomyelitis". World Health Organization (WHO).
  34. ^ "Polio and Prevention". Global Polio Eradication Initiative (GPEI). Retrieved 13 September 2015.
  35. ^ Pallansch MA (August 2018). "Ending Use of Oral Poliovirus Vaccine - A Difficult Move in the Polio Endgame". N. Engl. J. Med. 379 (9): 801–803. doi:10.1056/NEJMp1808903. PMID 30157390.
  36. ^ Modlin JF (June 2010). "The bumpy road to polio eradication". N. Engl. J. Med. 362 (25): 2346–9. doi:10.1056/nejmp1005405. PMID 20573922.
  37. ^ Diop OM, Burns CC, Sutter RW, Wassilak SG, Kew OM (June 2015). "Update on Vaccine-Derived Polioviruses - Worldwide, January 2014-March 2015" (PDF). Morbidity and Mortality Weekly Report (MMWR). 64 (23): 640–6. PMC 4584736. PMID 26086635.
  38. ^ a b c Imran Ali Teepu (26 February 2012). "WHO rejects polio rumours". Dawn. Retrieved 3 June 2012.
  39. ^ a b c Warraich HJ (June 2009). "Religious opposition to polio vaccination". Emerging Infect. Dis. 15 (6): 978a–978. doi:10.3201/eid1506.090087. PMC 2727330. PMID 19523311.
  40. ^ a b Ghani, Isaac; Willott, Chris; Dadari, Ibrahim; Larson, Heidi J. (2013). "Listening to the rumours: What the northern Nigeria polio vaccine boycott can tell us ten years on". Global Public Health. 8 (10): 1138–1150. doi:10.1080/17441692.2013.859720. PMC 4098042. PMID 24294986.
  41. ^ a b c d e Njeru, Ian; Ajack, Yusuf; Muitherero, Charles; Onyango, Dickens; Musyoka, Johnny; Onuekusi, Iheoma; Kioko, Jackson; Muraguri, Nicholas; David, Robert (2016). "Did the call for boycott by the Catholic bishops affect the polio vaccination coverage in Kenya in 2015? A cross-sectional study". Pan African Medical Journal. 24: 120. doi:10.11604/pamj.2016.24.120.8986. PMC 5012825. PMID 27642458.
  42. ^ Walsh D (14 February 2007). "Polio cases jump in Pakistan as clerics declare vaccination an American plot". The Guardian. Peshawar. Retrieved 29 March 2014.
  43. ^ Larson H (27 May 2012). "The CIA's fake vaccination drive has damaged the battle against polio". The Guardian. Retrieved 3 June 2012.
  44. ^ "Bin Laden death: 'CIA doctor' accused of treason". BBC News Online. 6 October 2011. Retrieved 8 October 2011.
  45. ^ Imran Ali Teepu (2 March 2012). "American NGOs assail CIA over fake polio drive". Dawn. Retrieved 27 May 2012.
  46. ^ Guerin O (24 May 2012). "'Emergency plan' to eradicate polio launched". BBC News Online. Retrieved 27 May 2012.
  47. ^ Shah S (2 March 2012). "CIA tactics to trap Bin Laden linked with polio crisis, say aid groups". The Guardian. Retrieved 27 May 2012.
  48. ^ Ahmed, Ali; Lee, Kah S.; Bukhsh, Allah; Al-Worafi, Yaser M.; Sarker, Moklesur; Ming, Long C.; Khan, Tahir M. (2018). "Outbreak of vaccine-preventable diseases in Muslim majority countries". Journal of Infection and Public Health. 11 (2): 153–155. doi:10.1016/j.jiph.2017.09.007. PMID 28988775.
  49. ^ Grossman S, Phillips J, Rosenzweig L (23 August 2016). "Polio is back in Nigeria, and the next vaccination campaign may have a surprising consequence". The Washington Post. Retrieved 23 August 2016.
  50. ^ "Protesting health workers threaten to boycott anti-polio drive". Dawn. 5 September 2015. Retrieved 23 August 2016.
  51. ^ "Up in arms: EPI workers threaten to boycott polio drives in FATA". Express Tribune. 26 April 2016. Retrieved 23 August 2016.
  52. ^ Sparrow A (20 February 2014). "Syria's Polio Epidemic: The Suppressed Truth". The New York Review of Books. Retrieved 31 August 2018.
  53. ^ a b "WHO Removes Nigeria from Polio-Endemic List". World Health Organization (WHO) (Press release). Retrieved 10 October 2017.
  54. ^ a b "The poliovirus transmission in Lao People's Democratic Republic has ceased" (Press release). World Health Organization (WHO). 6 March 2017. Retrieved 4 April 2017.
  55. ^ a b c "Government of Nigeria reports 2 wild polio cases, first since July 2014". World Health Organization (WHO). Retrieved 25 August 2018.
  56. ^ a b McCarthy, Kevin A.; Chabot-Couture, Guillaume; Shuaib, Faisal (29 September 2016). "A spatial model of Wild Poliovirus Type 1 in Kano State, Nigeria: calibration and assessment of elimination probability". BMC Infectious Diseases. 16 (1): 521. doi:10.1186/s12879-016-1817-3. ISSN 1471-2334. PMC 5041410. PMID 27681708.
  57. ^ a b Kalkowska DA, Duintjer Tebbens RJ, Pallansch MA, Cochi SL, Wassilak SG, Thompson KM (18 February 2015). "Modeling undetected live poliovirus circulation after apparent interruption of transmission: implications for surveillance and vaccination". BMC Infectious Diseases. 15: 66. doi:10.1186/s12879-015-0791-5. ISSN 1471-2334. PMC 4344758. PMID 25886823.
  58. ^ "Case 5: Eliminating Polio in Latin America and the Caribbean" (PDF). Center for Global Development (CGD). Retrieved 10 October 2017.
  59. ^ "Surveillance Indicators". Global Polio Eradication Initiative (GPEI). Retrieved 25 March 2018.
  60. ^ Cowger TL, Burns CC, Sharif S, Gary HE, Iber J, Henderson E, Malik F, Zahoor Zaidi SS, Shaukat S, Rehman L, Pallansch MA, Orenstein WA (25 July 2017). "The role of supplementary environmental surveillance to complement acute flaccid paralysis surveillance for wild poliovirus in Pakistan - 2011-2013". PLOS ONE. 12 (7): e0180608. Bibcode:2017PLoSO..1280608C. doi:10.1371/journal.pone.0180608. ISSN 1932-6203. PMC 5526532. PMID 28742803.
  61. ^ Roberts L (11 January 2018). "'What the hell is going on?' Polio cases are vanishing in Pakistan, yet the virus won't go away". Science. doi:10.1126/science.aas9789.
  62. ^ "This Man Has Been Shedding The Polio Virus For 28 Years". IFLScience. Retrieved 25 March 2018.
  63. ^ Miles T (23 October 2015). "WHO experts signal victory over one of three polio strains". Reuters. Retrieved 10 October 2017.
  64. ^ Global Commission for the Certification of Poliomyelitis Eradication (GCC) Report from the Sixteenth Meeting (PDF) (Report). Global Commission for the Certification of Poliomyelitis Eradication. September 2017.
  65. ^ "Global Eradication of Wild Poliovirus Type 2 Declared". Global Polio Eradication Initiative (GPEI). 20 September 2015. Retrieved 10 October 2017.
  66. ^ a b Lee, Jong Wook (1995). "Ending polio—now or never?". The Progress of Nations. Unicef. Archived from the original on 5 January 2018. Retrieved 2 February 2007.
  67. ^ Aylward RB, Linkins J (April 2005). "Polio eradication: mobilizing and managing the human resources" (PDF). Bull. World Health Organ. 83 (4): 268–73. hdl:10665/73115. PMC 2626205. PMID 15868017.
  68. ^ a b c d e f g h i "AFP/Polio Case Count". World Health Organization (WHO). 6 January 2015. Retrieved 10 January 2015.
  69. ^ a b "Wild poliovirus list". Global Polio Eradication Initiative (GPEI). Retrieved 23 February 2018.
  70. ^ 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.
  71. ^ Hinman AR (1984). "Landmark perspective: Mass vaccination against polio". JAMA. 251 (22): 2994–6. doi:10.1001/jama.1984.03340460072029. PMID 6371280.
  72. ^ a b c d Fujimura SF (2005). "The Man Who Made Polio History". Pan American Health Organization. Retrieved 2 February 2007.
  73. ^ "The End of Polio: Photographs of Sebastião Salgado Opens to Public" (Press release). Centers for Disease Control and Prevention (CDC). 24 August 2007. Retrieved 2 June 2008.
  74. ^ Centers for Disease Control and Prevention (CDC) (October 1994). "Certification of poliomyelitis eradication--the Americas, 1994" (PDF). Morbidity and Mortality Weekly Report (MMWR). 43 (39): 720–2. PMID 7522302.
  75. ^ "Pulse Polio Programme" (PDF). Government of India; Department of Family Welfare. 2013. Retrieved 10 July 2014.
  76. ^ "Operation MECACAR". World Health Organization (WHO). 2 June 2006. Archived from the original on 29 July 2007. Retrieved 2 February 2007.
  77. ^ "WHO European Region celebrates three polio-free years: certification within reach in 2002" (Press release). World Health Organization (WHO). 30 November 2001. Archived from the original on 22 September 2005. Retrieved 31 July 2007.
  78. ^ a b Yamazaki, S.; Toraya, H. (2001). "(General News) Major Milestone reached in Global Polio Eradication: Western Pacific Region is certified Polio-Free" (PDF). Health Educ. Res. 16 (1): 110–114. Bibcode:2001PDiff..16..110Y. doi:10.1154/1.1351153.
  79. ^ a b "Global Eradication Of Wild Poliovirus Type 2 Declared". Global Polio Eradication Initiative (GPEI). Retrieved 27 September 2015.
  80. ^ "CORE Group Polio Eradication Initiative". Archived from the original on 27 February 2009. Retrieved 10 March 2009.
  81. ^ "PolioPlus Timeline". Rotary International. Archived from the original on 20 February 2011. Retrieved 11 March 2011.
  82. ^ "Europe achieves historic milestone as Region is declared polio-free" (Press release). World Health Organization (WHO). 21 June 2002. Archived from the original on 16 May 2010. Retrieved 2 February 2007.
  83. ^ "WHO Director-General calls India 'number 1' polio eradication priority". World Health Organization (WHO) (Press release). 7 April 2003. Retrieved 31 July 2007.
  84. ^ 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.
  85. ^ "Sudan: Bulletin No. 28". International Committee of the Red Cross (ICRC). 11 May 2005. Retrieved 7 February 2007.
  86. ^ a b c d e f g "Wild Poliovirus List 2005-2011" (PDF). Global Polio Eradication Initiative (GPEI). 3 January 2012. Retrieved 13 September 2015.
  87. ^ "WHO Vaccine Preventable Diseases: Monitoring system" (XLS). World Health Organization (WHO). 2014. Retrieved 21 October 2014.
  88. ^ a b Balint-Kurti D (4 May 2005). "Polio Spreads From Nigeria After Claims". Associated Press. Retrieved 19 January 2013.
  89. ^ Aglionby J (2 September 2005). "Indonesia faces polio challenge". The Guardian. Retrieved 7 February 2007.
  90. ^ Centers for Disease Control and Prevention (October 2005). "Poliovirus infections in four unvaccinated children--Minnesota, August-October 2005" (PDF). Morbidity and Mortality Weekly Report (MMWR). 54 (41): 1053–5. PMID 16237378.
  91. ^ "Bangladesh begins new polio drive". BBC News Online. 2 March 2007. Retrieved 31 July 2007.
  92. ^ "First Lady of Nigeria inaugurates vaccination campaigns". Global Polio Eradication Initiative (GPEI). 30 July 2007. Archived from the original on 9 December 2007. Retrieved 24 January 2008.
  93. ^ Yusufzai A (30 July 2007). "Pakistan polio case in Australia". BBC News Online. Retrieved 8 August 2007.
  94. ^ "WHO Wild Poliovirus List" (PDF). Global Polio Eradication Initiative (GPEI). Archived from the original (PDF) on 18 May 2013. Retrieved 3 February 2013.
  95. ^ a b c "Wild Poliovirus 2010–2015" (PDF). Global Polio Eradication Initiative (GPEI). 9 September 2015. Archived from the original (PDF) on 28 September 2015. Retrieved 12 September 2015.
  96. ^ Choudary A (27 January 2013). "Pakistan close to getting rid of a polio virus: WHO". Dawn.com. Retrieved 29 March 2014.
  97. ^ Callaway E (13 May 2013). "Somalia records its first wild polio case since 2007". Nature News Blog. Retrieved 30 September 2015.
  98. ^ "Somalia hit by severe polio outbreak". BBC News Online. 16 August 2013. Retrieved 27 October 2019.
  99. ^ McNeil Jr DG (23 January 2013). "Egypt: Polio Virus Is Found in Cairo's Sewers". The New York Times. Retrieved 28 April 2013.
  100. ^ "Poliovirus detected from environmental samples in Israel". World Health Organization (WHO). 3 June 2013. Retrieved 30 September 2015.
  101. ^ Sterman A, Winer Jr S (12 June 2013). "More polio virus traces detected in Israel". Times of Israel. Retrieved 13 June 2013.
  102. ^ McNeil Jr DG (7 June 2013). "Polio Virus Discovered in Sewage From Israel". The New York Times. Retrieved 3 June 2013.
  103. ^ "Polio outbreak in Syria confirmed". BBC News Online. 29 October 2013. Retrieved 27 October 2019.
  104. ^ Nebehay S (11 November 2013). "Polio strain in Syria originated in Pakistan, WHO confirms". NBC News. Retrieved 12 November 2013.
  105. ^ Beaubien J (26 April 2013). "A $5.5 Billion Road Map To Banish Polio Forever". NPR. Retrieved 30 September 2015.
  106. ^ Khan D (16 October 2014). "Number of polio cases in Pakistan highest in 14 years". China Central TV. Retrieved 20 October 2014.
  107. ^ Semi-Annual Status Report, January-June 2014 (PDF) (Report). Global Polio Eradication Initiative (GPEI). Retrieved 11 June 2018.
  108. ^ Semi-Annual Status Report, July-December 2014 (PDF) (Report). Global Polio Eradication Initiative (GPEI). Retrieved 11 June 2018.
  109. ^ a b "WHO South-East Asia Region certified polio-free" (Press release). World Health Organization (WHO). 27 March 2014. Retrieved 27 March 2014.
  110. ^ "Polio-free certification: WHO South-East Asia". World Health Organization (WHO). 27 March 2014. Retrieved 27 March 2014.
  111. ^ Semi-Annual Status Report, January-June 2015 (PDF) (Report). Global Polio Eradication Initiative (GPEI). Retrieved 11 June 2018.
  112. ^ Semi-Annual Status Report, July-December 2015 (PDF) (Report). Global Polio Eradication Initiative (GPEI). Retrieved 11 June 2018.
  113. ^ "GPEI-Two out of three wild poliovirus strains eradicated". Retrieved 2 November 2019.
  114. ^ a b c d e f g "Polio Case Count". World Health Organization (WHO). 27 December 2017. Retrieved 27 December 2017.
  115. ^ Global Polio Eradication Initiative Annual Report 2016 (PDF) (Report). Global Polio Eradication Initiative (GPEI). Retrieved 24 June 2018.
  116. ^ Judd-Leonard Okafor (11 August 2016). "How polio returned to Nigeria". Daily Trust. Retrieved 11 August 2016.
  117. ^ "Circulating vaccine-derived poliovirus – Lao People's Democratic Republic". World Health Organization (WHO). Retrieved 9 February 2017.
  118. ^ "Semi-Annual Status Report: July to December 2016" (PDF). Global Polio Eradication Initiative (GPEI). p. 8. Retrieved 28 April 2017.
  119. ^ "Summary of poliovirus circulation in 2016 – Pakistan". World Health Organization (WHO). 27 December 2016.
  120. ^ Swaminathan K (15 June 2016). "Polio Strain Found in Hyderabad, India, Prompts Vaccination Drive". The New York Times. Retrieved 17 June 2016.
  121. ^ "Bomb near Pakistan polio centre 'kills 15'". BBC News Online. 13 January 2016. Retrieved 21 January 2016.
  122. ^ "Police Officers Guarding Polio Workers Killed in Karachi, Pakistan". NBC News. 20 April 2016. Retrieved 20 January 2016.
  123. ^ "Three Polio Workers Killed In Eastern Afghanistan". Radio Free Europe. 7 February 2016. Retrieved 20 April 2016.
  124. ^ "Global synchronisation and the switch". Global Polio Eradication Initiative (GPEI). Archived from the original on 15 May 2016. Retrieved 14 April 2016.
  125. ^ Martinez M, Shukla H, Nikulin J, Wadood MZ, Hadler S, Mbaeyi C, Tangermann R, Jorba J, Ehrhardt D (August 2017). "Progress Toward Poliomyelitis Eradication - Afghanistan, January 2016-June 2017" (PDF). Morbidity and Mortality Weekly Report (MMWR). 66 (32): 854–858. doi:10.15585/mmwr.mm6632a5. PMC 5657670. PMID 28817551.
  126. ^ Elhamidi, Youness; Mahamad, Abdirahman; Safdar, Muhammad; Al Tamimi, Wasan; Jorba, Jaume; Mbaeyi, Chukwuma; Hsu, Christopher H; Wadood, Zubair; Sharif, Salmaan; Ehrhardt, Derek (2017). "Progress Toward Poliomyelitis Eradication — Pakistan, January 2016–September 2017". Morbidity and Mortality Weekly Report (MMWR). 66 (46): 1276–1280. doi:10.15585/mmwr.mm6646a4. PMC 5769788. PMID 29166363.
  127. ^ Roberts L (11 January 2018). "'What the hell is going on?' Polio cases are vanishing in Pakistan, yet the virus won't go away". Science. doi:10.1126/science.aas9789. Retrieved 19 January 2018.
  128. ^ a b "Global Wild Poliovirus 2014 - 2019" (PDF). Global Polio Eradication Initiative (GPEI). Retrieved 3 February 2019.
  129. ^ Bolu O, Nnadi C, Damisa E, Braka F, Siddique A, Archer WR, Bammeke P, Banda R, Higgins J, Edukugo A, Nganda GW, Forbi JC, Liu H, Gidado S, Soghaier M, Franka R, Waziri N, Burns CC, Vertefeuille J, Wiesen E, Adamu U (March 2018). "Progress Toward Poliomyelitis Eradication — Nigeria, January–December 2017". Morbidity and Mortality Weekly Report (MMWR). 67 (8): 253–256. doi:10.15585/mmwr.mm6708a5. PMC 5861699. PMID 29494568.
  130. ^ Duizer, E.; Ruijs, W. L.; van der Weijden, C. P.; Timen, A. (2017). "Response to a wild poliovirus type 2 (WPV2)-shedding event following accidental exposure to WPV2, the Netherlands, April 2017". Eurosurveillance. 22 (21): 30542. doi:10.2807/1560-7917.ES.2017.22.21.30542. PMC 5479986. PMID 28597830.
  131. ^ "End of Outbreak in Lao Peoples Democratic Republic". Global Polio Eradication Initiative (GPEI). 29 May 2017. Retrieved 29 May 2017.
  132. ^ Herriman R (25 May 2017). "Polio update: Two cVDPV2 outbreaks reported in Democratic Republic of the Congo". Outbreak News Today. Retrieved 25 May 2017.
  133. ^ Alleman, Mary M; Chitale, Rohit; Burns, Cara C; Iber, Jane; Dybdahl-Sissoko2, Naomi; Chen, Qi; Van Koko, Djo-Roy; Ewetola, Raimi; Riziki, Yogolelo; Kavunga-Membo, Hugo; Dah, Cheikh; Andriamihantanirina, Rija (2018). "Vaccine-Derived Poliovirus Outbreaks and Events — Three Provinces, Democratic Republic of the Congo, 2017". Morbidity and Mortality Weekly Report (MMWR). 67 (10): 300–305. doi:10.15585/mmwr.mm6710a4. PMC 5857197. PMID 29543791.
  134. ^ a b "Circulating vaccine-derived poliovirus type 2 – Democratic Republic of the Congo". World Health Organization (WHO). 10 July 2018. Retrieved 13 August 2018.
  135. ^ a b c Mbaeyi, Chukwuma; Alleman, Mary M.; Ehrhardt, Derek; Wiesen, Eric; Burns, Cara C.; Liu, Hongmei; Ewetola, Raimi; Seakamela, Lerato; Mdodo, Rennatus; Ndoutabe, Modjirom; Kandolo Wenye, Pierre; Riziki, Yogolelo; Borus, Peter; Kamugisha, Christopher; Wassilak, Steven G. F. (2019). "Update on Vaccine-Derived Poliovirus Outbreaks — Democratic Republic of the Congo and Horn of Africa, 2017–2018". Morbidity and Mortality Weekly Report (MMWR). 68 (9): 225–230. doi:10.15585/mmwr.mm6809a2. PMC 6421971. PMID 30845121.
  136. ^ Branswell H (8 June 2017). "Polio outbreak is reported in Syria, WHO says". STAT. Retrieved 8 June 2017.
  137. ^ "WHO says child from Raqqa among 15 new polio cases in Syria". Reuters. 20 June 2017. Retrieved 20 June 2017.
  138. ^ a b "Circulating vaccine-derived poliovirus type 2 – Somalia". World Health Organization (WHO). 9 March 2018. Retrieved 21 October 2018.
  139. ^ "Summary of the April 2017 meeting of the Strategic Advisory Group of Experts on Immunization" (PDF). World Health Organization (WHO). Retrieved 15 May 2017.
  140. ^ Branswell H (19 May 2017). "As hopes for polio eradication rise, the endgame gets complicated, and a vaccine runs short". STAT. Retrieved 19 May 2017.
  141. ^ "WHO urges polio vaccine dose cut amid shortage". Business Insider. Agence France-Presse. 28 April 2017. Retrieved 28 October 2019.
  142. ^ a b c d e f g h i j k l m n "Polio This Week". Global Polio Eradication Initiative (GPEI).
  143. ^ "Pakistan". www.emro.who.int. Retrieved 24 January 2019.
  144. ^ "Pakistan Polio Update, December 2018". Global Polio Eradication Initiative (GPEI). Retrieved 31 January 2019.
  145. ^ User S. "Pakistan Polio Update". www.endpolio.com.pk. Retrieved 23 February 2019.
  146. ^ Hsu, Christopher; Mahamud, Abdirahman; Safdar, Muhammad; Nikulin, Johanna; Jorba, Jaume; Bullard, Kelley; Agbor, John; Kader, Milhia; Sharif, Salmann; Ahmed, Jamal; Ehrharst, Derek (2018). "Progress Toward Poliomyelitis Eradication — Pakistan, January 2017–September 2018". Morbidity and Mortality Weekly Report (MMWR). 67 (44): 1242–1245. doi:10.15585/mmwr.mm6744a5. PMC 6223954. PMID 30408024.
  147. ^ "Afghanistan Polio Snapshot – December 2018". Global Polio Eradication Initiative (GPEI). 31 December 2018.
  148. ^ Martinez, Maureen; Shukla, Hemant; Ahmadi, Meiland; Inulin, Joanna; Widodo, Mufti Sabari; Ahmed, Jamal; Mbaeyi, Chukwuma; Jabra, Jaime; Gerhardt, Derek (2018). "Progress Toward Poliomyelitis Eradication — Afghanistan, January 2017–May 2018". Morbidity and Mortality Weekly Report (MMWR). 67 (30): 833–837. doi:10.15585/mmwr.mm6730a6. PMC 6072060. PMID 30070983.
  149. ^ Martinez, Maureen; Shukla, Hemant; Nikulin, Joanna; Mbaeyi, Chukwuma; Jabra, Jaime; Ehrhardt (2019). "Progress Toward Poliomyelitis Eradication — Afghanistan, January 2018–May 2019". Morbidity and Mortality Weekly Report (MMWR). 68 (33): 729–733. doi:10.15585/mmwr.mm6833a4. PMC 6705892. PMID 31437144.
  150. ^ "Circulating vaccine-derived poliovirus type 2 – Nigeria". World Health Organization (WHO). 8 August 2018. Retrieved 13 August 2018.
  151. ^ Somalia cVDPV Outbreak Response Situation Report #3 (PDF) (Report). WHO, UNICEF. 20 August 2018. Retrieved 25 August 2018.
  152. ^ "Polio outbreak confirmed in Mozambique". Global Polio Eradication Initiative (GPEI). 8 January 2019. Retrieved 27 October 2019.
  153. ^ Mbaeyi, Chukwuma; Wadood, Zubair Mufti; Moran, Thomas Moran; Ather, Fazal; Stehling-Ariza, Tasha; Nikulin, Joanna; Al Dafadi, Mohammad; Iber, Jane; Zomahoun, Laurel; Abourshaid, Nidal; Pang, Hong; Collins, Nikki; Asghar, Humayun; Butt, Obaid ul Islam; Burns, Cara C.; Ehrhardt, Derek; Sharaf, Magdi (2018). "Strategic Response to an Outbreak of Circulating Vaccine-Derived Poliovirus Type 2 — Syria, 2017–2018". Morbidity and Mortality Weekly Report (MMWR). 67 (24): 690–694. doi:10.15585/mmwr.mm6724a5. PMC 6013082. PMID 29927908.
  154. ^ Papua New Guinea Polio Outbreak Response 2018 (PDF) (Report). World Health Organization (WHO). 2019.
  155. ^ a b "Global Wild Poliovirus 2014 - 2019" (PDF). Global Polio Eradication Initiative (GPEI). 22 October 2019.
  156. ^ Roberts L (10 July 2019). "Surging cases have dashed all hope that polio might be eradicated in 2019". Science. doi:10.1126/science.aay6925.
  157. ^ a b McNeil Jr DG (24 May 2019). "To Calm Nervous Families, Pakistan Changes Polio Vaccination Tactics". The New York Times. Retrieved 30 May 2019.
  158. ^ "Statement of the Twentieth IHR Emergency Committee". World Health Organization (WHO). Retrieved 16 March 2019.
  159. ^ Ahmed N (20 February 2019). "Polio spreads in Afghanistan and Pakistan 'due to unchecked borders'". The Guardian. Retrieved 20 February 2019.
  160. ^ "How to Cut a Long Story Short (Sixteenth Report of the Independent Monitoring Board)" (PDF). Global Polio Eradication Initiative (GPEI). October 2018. Retrieved 3 March 2019.
  161. ^ Constable P, Khan HN (5 March 2019). "Pakistan, on verge of eradicating polio virus, faces human hurdles". The Washington Post. Retrieved 7 March 2019.
  162. ^ Saifi S, Shah S (26 April 2019). "Pakistan's anti-vaccination movement leads to string of deadly attacks". CNN. Retrieved 26 April 2019.
  163. ^ Schnirring L (17 May 2019). "Four new polio cases in Pakistan as study tackles partial-dose vaccination". Center for Infectious Disease Research and Policy (CIDRAP). Retrieved 17 May 2019.
  164. ^ Adamu US, Archer WR, Braka F, Damisa E, Siddique A, Baig S, Higgins J, Sume GE, Banda R, Korir CK, Waziri N, Gidado S, Bammeke P, Edukugo A, Nganda GW, Forbi JC, Burns CC, Liu H, Jorba J, Asekun A, Franka R, Wassilak SG, Bolu O (July 2019). "Progress Toward Poliomyelitis Eradication - Nigeria, January 2018-May 2019". Morbidity and Mortality Weekly Report (MMWR). 68 (29): 642–646. doi:10.15585/mmwr.mm6829a3. PMC 6660103. PMID 31344023.
  165. ^ "Two out of three wild poliovirus strains eradicated". Global Polio Eradication Initiative (GPEI). Retrieved 24 October 2019.
  166. ^ "Mapped: Where polio lives in 2019". The New Humanitarian. 24 October 2019. Retrieved 2 November 2019.
  167. ^ Circulating vaccine-derived poliovirus type 2 – African Region (Report). World Health Organization (WHO). 31 July 2019. Retrieved 3 August 2019.
  168. ^ Hunt K (19 September 2019). "Polio makes a comeback in the Philippines 19 years after the country was declared free of the disease". CNN. Retrieved 19 September 2019.
  169. ^ Hughes C (19 September 2019). "Labs confirm 1st new case of polio in Philippines in 26 years". United Press International (UPI). Retrieved 19 September 2019.
  170. ^ UNICEF-WHO Philippines: Polio Outbreak Situation Report #9 (9 November 2019) (Report). UNICEF/WHO. 9 November 2019.

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